A: Chemical Bonding 1 Understanding Chemical Compounds, Stopped At Page 111 Flashcards
(519 cards)
1
Q
What are structural formulas also called?
A
Line formulas and structural diagrams.
2
Q
What do structural formulas show that molecular formulas do not?
A
Which atoms are bonded to each other.
3
Q
Why are bonding concepts in chemistry considered theoretical?
A
Because they are based on indirect experimental evidence and logic.
4
Q
Who stated that each element has a fixed bonding capacity?
A
Edward Frankland in 1852.
5
Q
What did Friedrich Kekulé illustrate in 1858?
A
A bond as a dash between bonding atoms, leading to structural formulas.
6
Q
Who extended structural formulas to three dimensions?
A
Jacobus van’t Hoff and Joseph Le Bel.
7
Q
What phenomenon were van’t Hoff and Le Bel trying to explain?
A
Optical activity.
8
Q
What did Richard Abegg suggest in 1904 regarding bonding capacity?
A
It must be associated with an atom’s electron structure.
9
Q
What evidence made Abegg’s theory seem probable?
A
Rutherford’s evidence for the nuclear atom.
10
Q
What did Abegg theorize about the stability of noble gases?
A
It was due to the number of electrons in the atom.
11
Q
How did Abegg explain the behavior of chlorine in reactions?
A
A chlorine atom is likely to gain one electron to form a stable chloride ion.
12
Q
What should a sodium atom do according to Abegg’s theory?
A
Lose one electron to form a stable sodium ion.
13
Q
What type of bond forms between sodium and chlorine atoms?
A
Ionic bonding.
14
Q
What is the force holding ions together in ionic bonding called?
A
Electrostatic forces.
15
Q
Fill in the blank: The newly formed ions in ionic bonding form visible _______.
A
Crystals of table salt.
16
Q
What effect does polarized light have when passing through polarized lenses?
A
It produces beautiful effects when passing through certain substances.
Polarized lenses, like those in sunglasses, filter light to reduce glare.
17
Q
Who proposed the concept of covalent bonds and when?
A
Gilbert Lewis in 1916.
Lewis combined evidence from chemical formulas and the concept of valence to explain atomic stability.
18
Q
What is a covalent bond?
A
The simultaneous attraction of the nuclei of two atoms for shared valence electrons.
Covalent bonds occur when atoms share electrons to achieve stable electron arrangements.
19
Q
What are valence electrons?
A
Electrons in the highest energy level of an atom.
Valence electrons are crucial for forming bonds between atoms.
20
Q
What is an ionic bond?
A
The simultaneous attraction between positive and negative ions resulting from the transfer of one or more valence electrons.
Ionic bonds typically form between metals and nonmetals.
21
Q
Fill in the blank: A covalent bond involves the _______ of valence electrons between two atoms.
A
[sharing]
22
Q
Fill in the blank: Gilbert Lewis’s proposal was based on the concept of stable _______ numbers for atoms.
A
[electron]
23
Q
True or False: Covalent bonds only occur between atoms that are far apart.
A
False.
Covalent bonds require atoms to stay close together for the attraction to occur.
24
Q
What is the primary force responsible for covalent bonding?
A
Attraction force between shared valence electrons and the nuclei of the atoms.
This attraction allows atoms to achieve stable electron configurations.
25
What major change occurred in understanding molecular compounds due to Lewis's work?
Many molecular compounds became more understandable.
## Footnote
Lewis's theories provided a clearer framework for explaining chemical bonding.
26
What is the culmination of the work discussed in Chapter 3?
The brilliant synthesis of concepts with quantum mechanics.
27
What does quantum mechanics describe electrons in terms of?
Energy content.
28
How are orbitals described in quantum mechanics?
In terms of the calculated probability of an electron being at any given point relative to the atomic nucleus.
29
Who published 'The Nature of the Chemical Bond' in 1939?
Dr. Linus Pauling.
30
To whom did Dr. Linus Pauling dedicate his book?
Gilbert Lewis.
31
What significant explanation did Pauling's work provide?
Why certain electron arrangements are stable.
32
What does electron sharing cover according to Pauling's work?
A complete range from equal attraction to total transfer.
33
In what year did Dr. Pauling win his first Nobel Prize?
1954.
34
What criteria are used to value scientific theories like Pauling's?
How well they describe, explain, and predict.
35
What is a characteristic of an acceptable theory according to scientists?
Simplicity.
36
Did Einstein fully accept the theory of quantum mechanics?
False.
37
What aspect of quantum mechanics did Einstein admire despite his suspicions?
Its ability to describe, explain, and predict observations.
38
Fill in the blank: Quantum mechanics developed from Einstein's revolutionary theories of ______, energy, space, and time.
matter.
39
What is the atomic theory regarding valence electrons during chemical reactions?
Only the valence electrons occupying the highest energy level are involved in bonding changes
## Footnote
Electrons in lower energy levels remain essentially unchanged during a reaction.
40
What is an orbital in the context of atomic theory?
A specific volume of space where an electron of certain energy is likely to be found
## Footnote
Each orbital may contain two, one, or no electrons.
41
Why is the term 'orbital' considered an unfortunate choice?
It suggests that electrons are like little particles in an orbit, which is misleading
## Footnote
Electrons behave differently than classical particles.
42
What are valence orbitals?
The volumes of space occupied by electrons in an atom's highest energy level
## Footnote
These are crucial for understanding chemical bonding.
43
What is a bonding electron?
A single electron in a valence orbital that can be shared with another atom
## Footnote
This sharing process is fundamental to chemical bonding.
44
What effect does a full valence orbital have on nearby electrons?
It has a repelling effect on electrons in any nearby orbitals
## Footnote
This repulsion is due to the presence of two electrons in the same orbital.
45
What are lone pairs?
Two electrons occupying the same orbital
## Footnote
Lone pairs play a significant role in molecular geometry and bonding.
46
Fill in the blank: According to quantum mechanics, an orbital is a specific volume of space in which an electron of _______ is likely to be found.
[certain energy]
47
True or False: Electrons in lower energy levels are involved in bonding changes during a chemical reaction.
False
## Footnote
Only valence electrons in the highest energy level are involved.
48
What classification is used for valence electrons based on orbital occupancy?
Valence electrons are classified as bonding electrons or lone pairs
## Footnote
This classification helps in understanding their role in bonding.
49
What is the maximum number of electrons in the first energy level?
2
## Footnote
The first energy level has room for only one orbital with a maximum of two electrons.
50
Which atom has only one energy level?
Hydrogen
## Footnote
Hydrogen is the smallest reactive atom with the simplest structure.
51
What is the significance of the octet rule?
Stability of valence electron configuration
## Footnote
The octet rule indicates that a structure with eight electrons filling a valence level is very stable.
52
Which elements are known to always obey the octet rule when bonding?
C, N, O
## Footnote
These are the main group atoms that consistently follow the octet rule.
53
What is the Pauli exclusion principle?
No more than two electrons may occupy the same orbital
## Footnote
This principle was first stated by Wolfgang Pauli in 1925.
54
What happens to electrons in empty orbitals according to quantum mechanics?
Electrons spread out to occupy any empty orbitals before forming pairs
## Footnote
This behavior is part of the theoretical definitions of orbitals.
55
How many orbitals are in energy levels above the first?
Four orbitals
## Footnote
Energy levels above the first can hold up to eight electrons.
56
What is the electronic structure of noble gases?
Filled valence level with eight electrons
## Footnote
This configuration leads to their lack of reactivity.
57
Fill in the blank: The first energy level contains only _______.
one orbital
58
True or False: Hydrogen follows the octet rule.
False
## Footnote
Hydrogen is an exception to most rules and generalizations that apply to other atoms.
59
What did Gilbert Lewis create to model the arrangement of electrons in atoms?
Lewis Symbols
## Footnote
This model explains and predicts empirical formulas.
60
In a Lewis symbol, what does the symbol for the element represent?
The nucleus plus all the electrons except the valence electrons
## Footnote
This collection of subatomic particles has a net positive charge.
61
How are valence electrons represented in a Lewis symbol?
As dots around the central symbol
## Footnote
The entire diagram shows a net charge of zero for the atom.
62
What is the net charge of a Lewis symbol diagram for an atom?
Zero
## Footnote
This indicates that the number of positive charges balances the negative charges.
63
What does the Lewis symbol for the oxygen atom indicate about its electrons?
It has two lone pairs and two bonding electrons
## Footnote
These are represented in its four valence orbitals.
64
What is the first step to draw Lewis symbols for main group atoms?
Write the element symbol to represent the nucleus and any filled energy levels of the atom
## Footnote
This establishes the basic structure of the Lewis symbol.
65
How are valence electrons added to the Lewis symbol?
By adding a dot for each valence electron
## Footnote
Start by placing valence electrons singly into each of the four valence orbitals.
66
How many valence electrons can be represented in the Lewis symbol?
Up to eight valence electrons
## Footnote
This is achieved by filling each of the four orbitals with a second electron until eight are represented.
67
True or False: The Lewis symbol model is one of many models used to represent the structure of an atom.
True
## Footnote
Other models include energy level diagrams.
68
Fill in the blank: The Lewis symbol for an atom shows its _______.
valence electrons
## Footnote
These electrons are critical for understanding how atoms bond.
69
What does the oxygen atom's Lewis symbol specifically represent?
The symbol O represents the oxygen nucleus and the two electrons in the first energy level
## Footnote
The net charge of the oxygen atom is 6.
70
What do Lewis symbols represent?
The arrangement of valence electrons around an atom's symbol
## Footnote
Lewis symbols are simplistic 2-D diagrams of complex 3-D structures that help visualize and account for each electron.
71
True or False: Lewis symbols indicate that electrons are stationary.
False
## Footnote
Lewis symbols do not mean that electrons are dots or that they are stationary.
72
What do the four sides of the atomic symbol in Lewis symbols represent?
The four valence level space regions (orbitals) that may be occupied by electrons
## Footnote
The dots in Lewis symbols keep count of how many electrons are in each orbital.
73
Define electronegativity.
The relative ability of an atom to attract a pair of bonding electrons in its valence level
## Footnote
Electronegativity is assigned based on an empirical scale developed by Linus Pauling.
74
According to Pauling's electronegativity scale, which element has the highest electronegativity?
Fluorine
## Footnote
Fluorine has an electronegativity of 4.0.
75
Which element has the lowest electronegativity among nonradioactive metals?
Cesium
## Footnote
Cesium has an electronegativity of 0.8.
76
Fill in the blank: Metals tend to have ______ electronegativities.
low
## Footnote
Nonmetals tend to have high electronegativities.
77
What factors influence an atom's ability to attract valence electrons?
* Distance from the nucleus
* Shielding by inner electrons
* Number of protons in the nucleus
## Footnote
These factors combine to assign a value to an atom's electronegativity.
78
Who developed the electronegativity scale?
Linus Pauling
## Footnote
Pauling's scale is based on energy changes in chemical reactions.
79
True or False: Nonmetals are typically more reactive than metals.
True
## Footnote
Fluorine is the most reactive nonmetal, while cesium is the least electronegative nonmetal.
80
What occurs when two atoms with half-filled orbitals collide?
Their orbitals overlap and a tug-of-war over the bonding electrons occurs.
81
What can predict which atom will capture the bonding electron in a collision?
The electronegativities of the two atoms.
82
What happens if the electronegativities of both atoms are relatively high?
Neither atom will win, and the bonding electrons will be shared.
83
What is the simultaneous attraction of two nuclei for a shared pair of bonding electrons called?
Covalent bond.
84
Between which types of atoms do covalent bonds normally form?
Two nonmetal atoms.
85
What type of substances are often produced when covalent bonds form during chemical reactions?
Molecular substances.
86
Fill in the blank: A covalent bond may involve _____ sharing of electrons between atoms.
equal or unequal
87
In covalent bonding, what happens to the electron sharing between two carbon atoms?
It is equal.
88
In covalent bonding, what happens to the electron sharing between a carbon atom and an oxygen atom?
It is unequal.
89
What happens when the electronegativities of two colliding atoms are quite different?
The atom with the stronger attraction for electrons may remove the bonding electron from the other atom, resulting in electron transfer and the formation of positive and negative ions.
90
What does the term ionic bond refer to?
The attraction between any specific cation and any specific anion.
91
What determines the numerical ratio of ions in an ionic compound?
The arrangement of ions in positions where the maximum total attraction between positive and negative charges occurs.
92
What is the numerical ratio of ions in calcium chloride (CaCl2)?
1:2.
93
What is the significance of the total net charge in ionic compounds?
The total net charge must become zero; extra negative charge would attract positive ions and vice versa.
94
What is the 3-D arrangement of ions in an ionic compound called?
Crystal lattice.
95
What is a characteristic feature of crystals formed by ionic compounds?
They always form in a regular, repeating 3-D pattern.
96
What predictable shape do ordinary table salt crystals form?
Cubic pattern.
97
What term describes the overall force holding together the ions in a crystal?
Ionic bonding.
98
True or False: The structure of ionic compounds is always non-crystalline.
False.
99
Fill in the blank: The bonding in ionic compounds involves enormous numbers of both kinds of ions and is not as simple as an ionic _______.
formula.
100
What occurs when two types of colliding atoms have relatively low electronegativities?
The atoms can share valence electrons without a chemical reaction taking place.
101
What is produced when melted lead and tin are mixed and cooled?
A solid called solder that is shiny, flexible, and conducts well.
102
What type of bonding occurs in substances like solder?
Metallic bond.
103
How are valence electrons treated in metallic bonding?
They are not held strongly by their atoms and are free to move about.
104
What do the positive nuclei of metal atoms do in metallic bonding?
They attract the mobile electrons between them.
105
How can the bonding in metallic substances be described?
As a great number of positive ions surrounded by a sea of mobile electrons.
106
What is the role of valence electrons in a metallic structure?
They act like glue that holds the whole structure together.
107
How does the attractive force around a metal atom act?
It acts in every direction.
108
How does the attractive force in metallic bonding compare to ionic and covalent bonding?
It is unlike ionic bonding, which has directional attraction, and covalent bonding, which acts only in one location.
109
What allows metal atoms in solid metals to move around each other?
The bonds between them are not weakened or broken by changing the shape of the solid.
110
What properties result from the mobility of valence electrons in metals?
* Ductility
* Malleability
* Ability to be formed into various shapes.
111
Since when has making objects from metal defined human technology?
Since the Bronze Age.
112
What were some uses of metals during the Bronze Age?
* Edged weapons
* Armor that did not break.
113
What is the primary focus of Section 3.2?
The understanding of molecular elements and compounds in terms of their chemical bonding.
114
What evidence did early scientists use to determine the common forms of certain elements?
Gases react in simple ratios of whole numbers and Avogadro's theory regarding equal volumes of gases containing equal numbers of molecules.
115
Which elements are commonly found as diatomic molecules?
* Hydrogen (H2)
* Oxygen (O2)
* Nitrogen (N2)
* Halogens (e.g., F2, Cl2, Br2, I2)
116
What are the common forms of phosphorus and sulfur?
* Phosphorus (P4)
* Sulfur (S8)
117
What must an acceptable theory of molecular elements provide?
An explanation for evidence such as the behavior of diatomic molecules according to atomic theory.
118
What is the goal of bonding theory in relation to electrons?
To explain how atoms can obtain stable octets through electron transfer or sharing.
119
True or False: All molecular elements are diatomic.
False
120
Fill in the blank: Many molecular elements are _______ and some are _______.
[diatomic], [polyatomic]
121
What is the formula for hydrogen as a molecular element?
H2
122
What is the formula for chlorine as a molecular element?
Cl2
123
What is the formula for iodine as a molecular element?
I2
124
What is the formula for sulfur as a molecular element?
S8
125
What is the formula for phosphorus as a molecular element?
P4
126
What does bonding theory suggest about the attraction of two chlorine molecules?
It involves the simultaneous attraction of two atoms due to their electrons.
127
What type of molecules are chlorine molecules?
Diatomic
## Footnote
Chlorine molecules consist of two atoms.
128
What do Lewis formulas communicate?
Electron sharing and octet formation
## Footnote
Lewis formulas help visualize how electrons are shared in chemical bonds.
129
How many valence electrons do oxygen atoms have according to atomic theory?
Six
## Footnote
Oxygen atoms have six valence electrons which influence their bonding behavior.
130
What was initially inadequate in explaining the diatomic character of oxygen?
Molecular theory
## Footnote
Initially, molecular theory could not explain why oxygen exists as a diatomic molecule.
131
What concept was introduced to explain the bonding in diatomic oxygen?
Double bond
## Footnote
A double bond involves sharing two pairs of electrons between atoms.
132
What is the result of two oxygen atoms sharing a pair of electrons?
A double covalent bond
## Footnote
This allows both atoms to achieve a stable octet.
133
What does the concept of a triple bond explain?
Chemical formulas of compounds like hydrogen cyanide (CN)
## Footnote
A triple bond involves three pairs of electrons being shared.
134
What do Lewis formulas account for?
Valence electrons
## Footnote
Lewis formulas are a form of electron bookkeeping.
135
What type of information do Lewis formulas not provide?
Orbital shapes or electron locations
## Footnote
They focus on which electrons are involved in bonding rather than their spatial arrangement.
136
What does a single line in structural formulas represent?
A single covalent bond
## Footnote
This indicates a sharing of one pair of electrons between atoms.
137
What does a double line in structural formulas represent?
A double bond
## Footnote
A double bond involves two pairs of shared electrons.
138
What does a triple line in structural formulas represent?
A triple bond
## Footnote
A triple bond involves three pairs of shared electrons.
139
What gas is produced in double the volume compared to oxygen when water is decomposed by electricity?
Hydrogen
## Footnote
This is based on the electrolysis of water.
140
What type of compounds cannot usually be represented by a simplest ratio formula?
Molecular compounds
## Footnote
They differ from ionic compounds in representation.
141
What do simplest ratio formulas indicate?
Relative numbers of atoms or ions in a compound
## Footnote
They do not provide evidence for actual number or arrangement.
142
What is the simplest ratio formula for a compound composed of equal numbers of carbon and hydrogen atoms?
CH
## Footnote
This represents a molecular compound.
143
Which two compounds can be described by the simplest ratio formula CH?
* Acetylene, C2H2(g)
* Benzene, C6H6
## Footnote
These compounds have different structures but share the same simplest ratio formula.
144
What do molecular formulas accurately represent?
The actual composition of the smallest units of molecular compounds
## Footnote
This is different from the structure of ionic compounds.
145
What is a key difference between molecular compounds and ionic compounds?
Molecular compounds have distinct molecular formulas, while ionic compounds form a continuous crystal lattice
## Footnote
The entire ionic structure acts as one bonded unit.
146
What concepts are used to explain molecular formulas?
* Overlapping half-filled orbitals
* Differences in electronegativity
## Footnote
These concepts provide a logical explanation of molecular structure.
147
True or False: Molecular compounds can be represented by the simplest ratio formula like ionic compounds.
False
## Footnote
Molecular compounds require molecular formulas for accurate representation.
148
What is the empirical formula for water?
H₂O
## Footnote
The empirical formula represents the simplest whole-number ratio of elements in a compound.
149
How many hydrogen atoms are in a single molecule of water?
2
## Footnote
A water molecule consists of two hydrogen atoms and one oxygen atom.
150
What type of bond holds the hydrogen and oxygen atoms together in water?
Covalent bonds
## Footnote
Covalent bonds are strong, directional forces that form between atoms sharing electrons.
151
What is the role of bonding electrons in oxygen's stability?
They complete oxygen's stable octet
## Footnote
Oxygen requires two electrons to achieve a full outer shell, which is achieved through covalent bonding with hydrogen.
152
What does a molecular formula illustrate?
The arrangement of atoms bonded together
## Footnote
It shows how atoms are connected and helps test the explanatory power of bonding theories.
153
What is a double covalent bond?
Sharing of two pairs of electrons
## Footnote
This type of bond occurs between two atoms that share more than one pair of bonding electrons.
154
True or False: An oxygen atom requires two electrons to complete a stable octet.
True
## Footnote
This requirement is crucial for the formation of stable molecules involving oxygen.
155
Fill in the blank: A covalent bond in molecular compounds is a strong, _______ force within a complete structural unit.
directional
## Footnote
The directional nature of covalent bonds influences the shape and properties of molecules.
156
What is a triple covalent bond?
A bond involving two atoms sharing three pairs of electrons.
157
Is there empirical evidence for the formation of a bond involving more than three pairs of electrons?
No.
158
Which elements can form more than one kind of covalent bond?
* Carbon
* Nitrogen
* Oxygen
159
What is bonding capacity?
The maximum number of single covalent bonds that an atom can form, determined by its number of bonding electrons.
160
What is the covalent bonding capacity of nitrogen?
Three.
161
How many single bonds can nitrogen form?
Three single bonds, one single bond and one double bond, or one triple bond.
162
What is the bonding capacity of carbon?
Four.
163
How can carbon's bonding capacity be expressed?
* Four single bonds
* Two double bonds
* One single and one triple bond
* One double and two single bonds
164
What do many people mistakenly believe about science?
That it is very structured, with no room for human creativity.
165
Who is Dr. John Polanyi?
A Canadian Nobel Prize winner for chemistry.
166
Fill in the blank: The maximum number of single covalent bonds that an atom can form is known as its _______.
[bonding capacity]
167
True or False: All atoms can form only one type of covalent bond.
False.
168
What is a coordinate covalent bond?
A covalent bond in which one of the atoms donates both electrons.
## Footnote
This concept helps explain the structure of many molecules and polyatomic ions.
169
How is a coordinate covalent bond formed?
When a nitrogen atom overlaps a full valence orbital (its lone pair) with an empty (unoccupied) valence orbital of a boron atom.
## Footnote
The equation H:N: + B:H → H:NB:H illustrates this formation.
170
Do the properties of coordinate covalent bonds differ from those of normal covalent bonds?
No, the properties do not differ because all electrons are alike, regardless of their source.
171
In the context of Lewis formulas, what is irrelevant?
Which atom the electrons 'come from'.
172
What does the restricted theory discussed in the textbook state about valence electrons?
It requires that all valence electrons in molecules be paired.
173
Are there exceptions to the theory regarding paired valence electrons?
Yes, some molecules, such as nitrogen monoxide, have unpaired electrons.
174
What is an example of a molecule that does not follow the octet rule?
Boron trihydride.
175
What is emphasized about scientific theories in the textbook?
No theory in science is absolute and there are exceptions.
176
What is necessary to obtain an answer of note?
One must ask a question of note that is exquisitely phrased.
177
What is the significance of asking the right question in scientific inquiry?
It must be a question that matters, on a topic that is new, to which an answer can be found.
178
Who is John Polanyi?
A scientist born in 1929 mentioned in the textbook.
179
What does the term 'empirical' mean when referring to data?
Obtained by direct observation, such as in a laboratory
## Footnote
Empirical data is based on evidence collected through experiments and observations.
180
What is an empirical formula?
A formula that shows the whole-number ratio of atoms or ions present in a compound
## Footnote
Empirical formulas provide the simplest ratio of elements in a compound, not the actual number of atoms.
181
What is the significance of empirical formulas in ionic compounds?
They represent the crystal lattice with a formula unit that shows the simplest number ratio of cations to anions
## Footnote
The ion charges are omitted in empirical formulas for ionic compounds.
182
How is the molar mass of an ionic compound defined?
The mass of a mole of formula units
## Footnote
Molar mass is important for stoichiometric calculations in chemistry.
183
What is the difference between an empirical formula and a molecular formula?
An empirical formula shows the simplest whole-number ratio of atoms, while a molecular formula shows the actual number of atoms in a molecule
## Footnote
Molecular formulas provide detailed information about the composition of a molecule.
184
What is the molecular formula for acetic acid?
C2H4O2
## Footnote
This molecular formula illustrates the actual numbers of each type of atom in acetic acid.
185
Fill in the blank: An empirical formula shows the _______ of atoms in the compound.
simplest whole-number ratio
186
True or False: Empirical formulas are useful for molecular compounds.
False
## Footnote
Empirical formulas are rarely useful for molecular compounds as they do not provide detailed atomic information.
187
What do Lewis symbols represent in molecular formulas?
The sharing of electrons in covalent bond formation
## Footnote
Lewis symbols help visualize how atoms bond in molecular compounds.
188
What is a Lewis formula also commonly called?
A Lewis diagram or an electron-dot diagram
## Footnote
It shows electron sharing in covalent bonds and stable valence octets.
189
What does a structural formula represent?
The types of covalent bonds represented by the number of lines drawn between atomic symbols
## Footnote
It is also commonly called a structural diagram.
190
What is the purpose of a stereochemical formula?
To represent the three-dimensional molecular shape
## Footnote
It can become too complex for much larger molecules.
191
What have scientists been collecting evidence of for decades?
The shapes of molecules
## Footnote
This evidence has been converted into interactive models using software.
192
How have software engineers contributed to molecular science?
By converting scientific findings into interactive three-dimensional models
## Footnote
These models can be explored on various websites.
193
Fill in the blank: A Lewis formula uses _______ to show electron sharing.
[Lewis symbols]
194
True or False: A structural formula can show the types of covalent bonds.
True
195
What happens to the complexity of stereochemical formulas as molecules get larger?
They often become too complex to be practical
## Footnote
This complexity limits their usefulness for very large molecules.
196
What is a Lewis formula also commonly called?
A Lewis diagram or an electron-dot diagram
## Footnote
It shows electron sharing in covalent bonds and stable valence octets.
197
What does a structural formula represent?
The types of covalent bonds represented by the number of lines drawn between atomic symbols
## Footnote
It is also commonly called a structural diagram.
198
What is the purpose of a stereochemical formula?
To represent the three-dimensional molecular shape
## Footnote
It can become too complex for much larger molecules.
199
What have scientists been collecting evidence of for decades?
The shapes of molecules
## Footnote
This evidence has been converted into interactive models using software.
200
How have software engineers contributed to molecular science?
By converting scientific findings into interactive three-dimensional models
## Footnote
These models can be explored on various websites.
201
Fill in the blank: A Lewis formula uses _______ to show electron sharing.
[Lewis symbols]
202
True or False: A structural formula can show the types of covalent bonds.
True
203
What happens to the complexity of stereochemical formulas as molecules get larger?
They often become too complex to be practical
## Footnote
This complexity limits their usefulness for very large molecules.
204
What is the purpose of physical models in chemistry?
To help understand the shape, relative size, and structure of molecules
## Footnote
Physical models can include various kinds of diagrams and pictures to visualize molecular structures.
205
What does a Lewis formula predict?
Valence electron distribution and structure of molecules
## Footnote
Lewis formulas are particularly useful for predicting how atoms are bonded in a molecule.
206
What is the first step in determining the Lewis formula for a molecule?
Count the total valence electrons in the entity
## Footnote
This includes adding up the valence electrons of all atoms in the molecule.
207
Fill in the blank: A Lewis formula allows predictions of _______ structure.
entity
208
True or False: Lewis formula predictions are limited to simple entities.
True
## Footnote
Lewis formulas are often used for simple molecules and may not adequately represent more complex structures.
209
What is an example of a molecule for which a Lewis formula can be determined?
Sulfur trioxide (SO3)
## Footnote
The Lewis formula for sulfur trioxide can be derived by following the outlined steps.
210
What adjustment must be made when counting valence electrons for polyatomic ions?
Add or subtract valence electrons as necessary
## Footnote
The total count of valence electrons can change based on the charge of the ion.
211
What is the significance of the structural formula?
It represents the arrangement of atoms within a molecule
## Footnote
Structural formulas provide insight into how atoms are connected in a molecule.
212
What has been used to investigate the shape of molecules since the early 1900s?
X-ray and other spectrographic techniques
## Footnote
Crystallography, microscopes, and polarimeters were used in the late 1800s.
213
What is one of the most important applications of molecular shape research?
The study of enzymes
214
How many enzymes are there approximately in an average living cell?
About three thousand
215
What do enzymes do?
Catalyze specific reactions
216
What analogy is used to describe how enzymes interact with specific molecules?
Like a key's shape fits only one specific lock
217
What is the consequence of errors in molecular shapes for enzymes?
Affects the normal functioning of the cell
218
What is still effectively impossible to predict about enzymes?
The shape an enzyme will take
219
Who created and popularized the valence bond theory?
Linus Pauling
220
In what decade was the valence bond theory created?
Late 1930s
221
What did Pauling's empirical work primarily involve?
X-ray analysis of crystals
222
Who extended the work of Linus Pauling?
Gilbert Lewis
223
What are Lewis symbols also known as?
Electron-dot diagrams
224
What year did Ronald Nyholm and Ron Gillespie create a simpler theory for stereochemistry?
1957
225
What does stereochemistry study?
The 3-D spatial configuration of molecules
226
What is the primary role of biochemists?
Study the chemistry of living matter
227
In what areas do biochemists conduct research?
Medicine, agriculture, and environmental science
228
Fill in the blank: The theory created by Nyholm and Gillespie is highly effective for predicting the shape of _______.
Molecules
229
What does VSEPR stand for?
Valence-Shell-Electron-Pair-Repulsion
## Footnote
VSEPR theory helps predict the shape of molecules based on electron pair repulsion.
230
What is the main principle of VSEPR theory?
Electron pairs in the valence shell of an atom stay as far apart as possible due to repulsion of their negative charges
## Footnote
This principle helps in determining the three-dimensional arrangement of atoms in a molecule.
231
How do you count the number of electron pairs in VSEPR theory?
Add the number of bonded atoms plus the number of lone pairs of electrons
## Footnote
This count allows for predicting the molecular shape.
232
What determines the shape of the resulting molecule according to VSEPR theory?
The type, number, and direction of bonds to the central atom
## Footnote
These factors influence the arrangement of electron pairs.
233
True or False: Only the valence electrons of the central atom(s) are important for molecular shape.
True
## Footnote
This emphasizes the focus on the valence shell in determining molecular geometry.
234
What are the two types of electron pairs considered in VSEPR theory?
* Bonded pairs of electrons
* Lone pairs of electrons
## Footnote
Both types are treated approximately equally in the theory.
235
Fill in the blank: The molecular shape is determined by the positions of the electron pairs when they are at a _______.
maximum
## Footnote
This refers to the arrangement that minimizes repulsion between electron pairs.
236
Who co-created VSEPR theory and in what year?
Dr. Ronald Gillespie in 1957
## Footnote
His contributions significantly advanced the understanding of molecular geometry.
237
What is a common example of molecules with four electron pairs around the central atom?
* Ammonia molecule
* Water molecule
## Footnote
Both contain bonding and lone pairs of electrons surrounding the central atom.
238
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion
## Footnote
VSEPR theory is used to predict molecular shapes based on electron pair interactions.
239
What is the first step in using VSEPR theory to predict molecular shape?
Draw Lewis formulas of each of the molecules
## Footnote
Lewis formulas depict the arrangement of valence electrons in molecules.
240
According to VSEPR theory, how do valence electron pairs behave?
They repel each other and try to get as far from each other as possible
## Footnote
This repulsion influences the overall geometry of the molecule.
241
What is the shape of hydrogen compounds in Period 2 according to VSEPR theory?
Tetrahedral, trigonal planar, and linear
## Footnote
These shapes depend on the arrangement of valence electrons around the central atom.
242
Fill in the blank: The molecular formula for Beryllium Dihydride is _______.
BeH2
## Footnote
Beryllium Dihydride consists of one beryllium atom and two hydrogen atoms.
243
What is the molecular formula for Boron Trihydride?
BH3
## Footnote
Boron Trihydride contains one boron atom and three hydrogen atoms.
244
What does the arrangement of valence electrons determine in a molecule?
The molecular shape
## Footnote
Different arrangements lead to different geometric configurations.
245
True or False: VSEPR theory is only applicable to molecules with central atoms.
True
## Footnote
VSEPR theory primarily focuses on predicting the shapes of molecules with a central atom surrounded by electron pairs.
246
What is the Lewis formula for Methane (CH₄)?
H
H:C:H
H
247
How many total electron pairs are present in Methane?
4
248
What is the electron pair arrangement around the central atom in Methane?
tetrahedral
249
What is the stereochemical formula for Methane?
tetrahedral
250
What angle do the bonds in a tetrahedral arrangement make with each other?
109.5°
251
True or False: The tetrahedral arrangement minimizes electron pair repulsion.
True
252
According to VSEPR theory, what shape does the Methane molecule have?
tetrahedral
253
Fill in the blank: The classic shape of the Methane molecule is _______.
tetrahedral
254
What does the Lewis theory indicate about the bonding in Methane?
CH₄ has four bonds or four pairs of electrons repelling each other
255
What is the significance of the tetrahedral arrangement in Methane?
It minimizes the repulsion between electron pairs.
256
What is the Lewis formula for ammonia?
NH3 with three bonding pairs and one lone pair
## Footnote
The lone pair is represented by E in the general formula.
257
According to VSEPR theory, what is the electron pair arrangement for ammonia?
Tetrahedral
## Footnote
This arrangement is similar to that of methane (CH4).
258
What is the molecular geometry of ammonia?
Trigonal pyramidal
## Footnote
This shape is due to the presence of the lone pair.
259
What is the ideal bond angle for a tetrahedral arrangement?
109.5 degrees
## Footnote
However, the bond angle in ammonia is 107.3 degrees.
260
What is the bond angle in ammonia?
107.3 degrees
## Footnote
This angle is less than the ideal tetrahedral angle due to lone pair repulsion.
261
What causes the bond pairs in ammonia to be pushed closer together?
Stronger repulsion between the lone pair and bonding pairs
## Footnote
This is a key concept in VSEPR theory.
262
Who developed the VSEPR theory?
Ronald Gillespie
## Footnote
Gillespie has also contributed significantly to the study of acids.
263
Fill in the blank: The general formula for the electron pair arrangement is _______.
AXE
264
True or False: The shape of the ammonia molecule is a simple tetrahedron.
False
## Footnote
The shape is trigonal pyramidal due to the lone pair.
265
What type of molecular shape does ammonia resemble?
A three-sided (triangular) pyramid
## Footnote
This is referred to as trigonal pyramidal.
266
What is the shape of water molecules?
Angular, bent, or N-shaped
## Footnote
The most appropriate term is Dr. Gilespie's original word 'angular'.
267
What is the Lewis formula for water?
:O:H
## Footnote
This represents the bonding structure of water with oxygen and hydrogen.
268
How many bond pairs are present in a water molecule?
2
## Footnote
Water has two hydrogen atoms bonded to one oxygen atom.
269
How many lone pairs of electrons does water have?
2
## Footnote
These lone pairs are located on the oxygen atom.
270
What is the electron pair arrangement in water according to VSEPR theory?
Tetrahedral
## Footnote
This arrangement is due to the four pairs of electrons around the oxygen atom.
271
What is the geometry of the water molecule?
Angular
## Footnote
The geometry is defined by the bond angle of 104.5 degrees.
272
What is the bond angle in a water molecule?
104.5 degrees
## Footnote
This angle is less than the ideal tetrahedral angle of 109.5 degrees.
273
True or False: The ideal angle for a tetrahedral arrangement of electron pairs is 104.5 degrees.
False
## Footnote
The ideal angle is 109.5 degrees.
274
What causes the bond pairs in water to be closer together than in a perfect tetrahedral arrangement?
Slightly stronger repulsion exerted by lone pairs
## Footnote
Lone pairs repel more strongly than bonding pairs, resulting in a smaller bond angle.
275
What is the original word used by Gillespie in relation to molecular geometry?
angular
## Footnote
Refers to the geometry of molecules as described by Gillespie.
276
What type of atom is beryllium classified as?
metal
## Footnote
Despite being a metal, beryllium can form molecular compounds with nonmetals.
277
What compound is referenced in relation to beryllium?
Hydrogen Fluoride
## Footnote
Hydrogen fluoride (HF) is used to illustrate molecular geometry.
278
What is the Lewis formula for Hydrogen Fluoride?
H:F:
## Footnote
The Lewis formula represents the bonding in the molecule.
279
How many bonding pairs and lone pairs are in the hydrogen fluoride molecule according to Lewis theory?
1 bonding pair and 3 lone pairs
## Footnote
This configuration influences the molecular shape.
280
What is the electron pair arrangement for hydrogen fluoride as per VSEPR theory?
tetrahedral
## Footnote
The tetrahedral arrangement arises from electron pair repulsion.
281
What shape does VSEPR theory predict for the hydrogen fluoride molecule?
linear
## Footnote
Despite the tetrahedral arrangement of electrons, HF is linear due to its diatomic nature.
282
What does VSEPR theory describe, explain, and predict?
the geometry of the central atom
## Footnote
VSEPR theory is crucial for understanding molecular shapes.
283
What is the first step in predicting the shape of a molecule according to the process summarized?
Draw the Lewis formula for the molecule
## Footnote
This is essential for visualizing electron arrangements.
284
What is the second step in the process of predicting molecular shape?
Count the total number of bonding pairs and lone pairs of electrons around the central atom
## Footnote
Accurate counting is critical for determining the molecular geometry.
285
What is the third step in predicting the shape of a molecule?
Refer to Table 7 to predict the shape of the molecule
## Footnote
The table provides a guide based on the number of electron pairs.
286
What is the original word used by Gillespie in relation to molecular geometry?
angular
## Footnote
Refers to the geometry of molecules as described by Gillespie.
287
What type of atom is beryllium classified as?
metal
## Footnote
Despite being a metal, beryllium can form molecular compounds with nonmetals.
288
What compound is referenced in relation to beryllium?
Hydrogen Fluoride
## Footnote
Hydrogen fluoride (HF) is used to illustrate molecular geometry.
289
What is the Lewis formula for Hydrogen Fluoride?
H:F:
## Footnote
The Lewis formula represents the bonding in the molecule.
290
How many bonding pairs and lone pairs are in the hydrogen fluoride molecule according to Lewis theory?
1 bonding pair and 3 lone pairs
## Footnote
This configuration influences the molecular shape.
291
What is the electron pair arrangement for hydrogen fluoride as per VSEPR theory?
tetrahedral
## Footnote
The tetrahedral arrangement arises from electron pair repulsion.
292
What shape does VSEPR theory predict for the hydrogen fluoride molecule?
linear
## Footnote
Despite the tetrahedral arrangement of electrons, HF is linear due to its diatomic nature.
293
What does VSEPR theory describe, explain, and predict?
the geometry of the central atom
## Footnote
VSEPR theory is crucial for understanding molecular shapes.
294
What is the first step in predicting the shape of a molecule according to the process summarized?
Draw the Lewis formula for the molecule
## Footnote
This is essential for visualizing electron arrangements.
295
What is the second step in the process of predicting molecular shape?
Count the total number of bonding pairs and lone pairs of electrons around the central atom
## Footnote
Accurate counting is critical for determining the molecular geometry.
296
What is the third step in predicting the shape of a molecule?
Refer to Table 7 to predict the shape of the molecule
## Footnote
The table provides a guide based on the number of electron pairs.
297
What does AX represent in VSEPR theory?
A is the central atom; X represents surrounding atoms.
298
What is the molecular shape for AX2?
linear
299
What is the molecular shape for AX3?
trigonal planar
300
What is the molecular shape for AX4?
tetrahedral
301
What is the molecular shape for AX3E?
trigonal pyramidal
302
What is the molecular shape for AX2E2?
bent
303
Fill in the blank: Molecules with a ______ shape are better in mosquito repellents.
round
304
True or False: Research has shown that long, thin molecules are better at repelling mosquitoes.
False
305
What do round molecules block in mosquitoes?
sensory nerves in the antennae
306
What makes it difficult for mosquitoes to detect carbon dioxide, moisture, and heat?
round molecules blocking sensory nerves
307
What diseases can mosquitoes transmit?
* malaria
* West Nile fever
308
What does the acronym VSERR represent in relation to molecular geometry?
The acronym VSERR represents key concepts in VSEPR theory that communicate the main ideas of molecular geometry.
## Footnote
VSEPR stands for Valence Shell Electron Pair Repulsion.
309
Predict the geometry of ClO3 using VSEPR theory and state whether the central atom obeys the octet rule.
The geometry of ClO3 is trigonal pyramidal and the central atom does obey the octet rule.
## Footnote
The central chlorine atom has a total of eight electrons in its valence shell.
310
Predict the geometry of PF5 using VSEPR theory and state whether the central atom obeys the octet rule.
The geometry of PF5 is trigonal bipyramidal and the central atom does not obey the octet rule.
## Footnote
Phosphorus can expand its octet to accommodate more than eight electrons.
311
Predict the geometry of BrF3 using VSEPR theory and state whether the central atom obeys the octet rule.
The geometry of BrF3 is T-shaped and the central atom does obey the octet rule.
## Footnote
Bromine has three bonding pairs and two lone pairs.
312
Predict the geometry of SiBr4 using VSEPR theory and state whether the central atom obeys the octet rule.
The geometry of SiBr4 is tetrahedral and the central atom does obey the octet rule.
## Footnote
Silicon has four bonding pairs with no lone pairs.
313
Predict the shape of the polyatomic ion PO4^3- using VSEPR theory.
The shape of PO4^3- is tetrahedral.
## Footnote
The central phosphorus atom is bonded to four oxygen atoms.
314
Predict the shape of the polyatomic ion BrO3^- using VSEPR theory.
The shape of BrO3^- is trigonal pyramidal.
## Footnote
The bromine atom has one lone pair and three bonding pairs.
315
Predict the shape of the polyatomic ion NH4^+ using VSEPR theory.
The shape of NH4^+ is tetrahedral.
## Footnote
The nitrogen atom is bonded to four hydrogen atoms with no lone pairs.
316
What is the molecular formula of cubane?
The molecular formula of cubane is C8H8.
## Footnote
Cubane consists of eight carbon atoms and eight hydrogen atoms.
317
Describe the shape of cubane.
Cubane has a cubic shape with a carbon atom at each corner of the cube.
## Footnote
The structure implies a three-dimensional arrangement of carbon atoms.
318
Why is cubane considered very unstable?
Cubane is considered very unstable due to the high strain in its bond angles and structure.
## Footnote
Crystals of cubane have been known to explode under certain conditions.
319
According to VSEPR theory, what should be the shape around each carbon atom in cubane?
The shape around each carbon atom in cubane should be tetrahedral.
## Footnote
Each carbon atom is bonded to four hydrogen atoms.
320
Where did the evidence come from that led to the creation of VSEPR theory?
The evidence for VSEPR theory came from observations of molecular shapes and bond angles in various compounds.
## Footnote
Experimental data and theoretical predictions helped establish the principles of VSEPR.
321
What is a double bond or triple bond considered in VSEPR theory?
One bond
## Footnote
Always treat multiple bonds as single bonds when predicting molecular shapes.
322
How do hydrocarbons with multiple bonds react with bromine?
Rapidly, removing the orange-brown color of the reagent
## Footnote
This indicates their high reactivity compared to hydrocarbons with only single bonds.
323
What is the reactivity of hydrocarbon molecules with only single bonds?
Extremely slowly
## Footnote
This contrasts with those containing double or triple bonds.
324
How does a double bond or triple bond compare to a single bond in terms of strength and length?
Always shorter and stronger
## Footnote
This applies to bonds between the same kind of atoms.
325
What type of analysis provides evidence for the properties of multiple bonds?
Crystallography
## Footnote
Specifically, X-ray analysis of crystals helps in understanding bond characteristics.
326
What implication does the treatment of multiple bonds have on VSEPR theory?
Multiple bonds are treated like single bonds for shape prediction
## Footnote
This affects how molecular shapes are described and explained.
327
Fill in the blank: Hydrocarbons with double or triple bonds react ______ with bromine.
rapidly
328
Fill in the blank: Evidence shows that a double bond or triple bond is always ______ than a single bond.
stronger
329
True or False: Double bonds and triple bonds are treated differently than single bonds in VSEPR theory.
False
## Footnote
They are treated the same for predicting molecular shapes.
330
What is the stereochemical formula of ethyne?
H:C:H
## Footnote
Ethyne is also known as acetylene and has the molecular formula C2H2.
331
According to VSEPR theory, what is the shape of the ethyne molecule?
Linear
## Footnote
VSEPR theory stands for Valence Shell Electron Pair Repulsion theory, which predicts molecular shapes based on electron pair repulsions.
332
What is the stereochemical formula for a nitrite ion?
N
## Footnote
The nitrite ion (NO2-) has a central nitrogen atom bonded to two oxygen atoms.
333
What is the shape of the nitrite ion according to VSEPR theory?
Angular
## Footnote
The presence of a lone pair on the nitrogen atom influences the shape of the nitrite ion.
334
What does bonding theory suggest about ethene and ethyne?
Ethene has one double bond and ethyne has one triple bond
## Footnote
This relates to the types of covalent bonds formed in these hydrocarbons.
335
What empirical evidence supports bonding theory for ethene and ethyne?
Multiple covalent bonds are shorter than single bonds
## Footnote
X-ray crystallography is often used to measure bond lengths.
336
What discrepancy is noted in the prediction for the nitrite ion's bond types?
Both bonds are identical in length and strength
## Footnote
This contradicts the prediction of one single and one double bond based on the resonance structures.
337
What is a limitation of bonding theory as mentioned in the text?
Electrons are not really small particles
## Footnote
This highlights the complexity of electron behavior beyond classical particle models.
338
True or False: The bond type prediction for ethyne is accurate.
True
## Footnote
The bond type prediction for ethyne aligns with empirical data.
339
True or False: The shape prediction for the nitrite ion is inaccurate.
False
## Footnote
The shape prediction is accurate, but the bond type prediction is not.
340
Fill in the blank: According to VSEPR theory, a nitrite ion has an _______ shape.
Angular
341
What is a polar molecule?
A polar molecule is one in which the negative (electron) charge is not distributed symmetrically among the atoms making up the molecule.
342
What characterizes the charge distribution in a polar molecule?
It has partial positive and negative charges on opposite sides of the molecule.
343
What is a nonpolar molecule?
A molecule with symmetrical electron distribution.
344
How can the existence of polar molecules be demonstrated?
By running a stream of water past a charged object.
345
What does the experiment with pure liquids produce?
A set of empirical rules for predicting whether a molecule is polar.
346
Fill in the blank: A molecule with symmetrical electron distribution is a _______.
nonpolar molecule.
347
True or False: A polar molecule has an equal distribution of electron charge.
False.
348
What are the charged particles that make up molecules?
Electrons and nuclei.
349
What type of molecule is described as diatomic with different atoms?
AB
## Footnote
Examples include HCl(g) and CO(g)
350
What type of molecule contains nitrogen and other atoms?
N,A,
## Footnote
Examples include NH3(g) and NF3(g)
351
What type of molecule contains carbon and two other kinds of atoms?
CAB
## Footnote
An example is C2H5OH
352
What type of molecule contains oxygen and other atoms?
O
## Footnote
Examples include H2O and ClO2(g)
353
What type of molecule contains carbon and only one other kind of atom?
A
## Footnote
Examples include CO(g) and CH4(g)
354
What type of molecule is classified as nonpolar?
NonpolarA
## Footnote
Examples include N2(g) and Cl2(g)
355
What is electronegativity?
An atomic property that explains and predicts the polarity of molecular substances
## Footnote
It was created by Linus Pauling by combining valence bond theory, bond energy theory, and empirical measures.
356
How does electronegativity vary in the periodic table?
It increases as an atom's position is farther to the right in a row or higher up in a column
## Footnote
This is illustrated in Figure 10.
357
What determines the polarity of a covalent bond?
The difference in electronegativity of the bonded atoms
## Footnote
If the atoms have the same electronegativity, the bond is nonpolar.
358
What type of bond is formed when bonded atoms have the same electronegativity?
A nonpolar covalent bond
359
What type of bond is formed when bonded atoms have different electronegativities?
A polar covalent bond
360
What happens as the electronegativity difference increases?
The bond becomes more polar
## Footnote
A very large electronegativity difference can lead to the formation of cations and anions.
361
What is formed in an ionic compound?
Cations and anions held together by ionic bonding
362
In a polar covalent bond, what happens to the shared electrons?
They are attracted unequally by the two atoms
363
What is indicated by the lowercase delta in bond notation?
Partial charge
## Footnote
The side of the bond with a partial negative charge is denoted as δ-, and the side with a partial positive charge as δ+.
364
What does the side of the bond with higher electronegativity become?
Partially negative
365
What does the side of the bond with lower electronegativity become?
Partially positive
366
What is the primary concept Pauling believed regarding chemical bonds?
Chemical bonds are different in degree rather than different in kind.
367
What do all chemical bonds involve according to Pauling?
A sharing of electrons.
368
What are the two extreme cases of chemical bonds as per Pauling's view?
* Ionic bonds
* Nonpolar covalent bonds
369
What does the bonding in substances range along?
A continuum from nonpolar covalent to polar covalent to ionic.
370
In polar covalent bonds, what does a greater electronegativity difference indicate?
A more polar bond.
371
Fill in the blank: The bonding in substances ranges along a continuum from _______ to polar covalent to ionic.
nonpolar covalent
372
True or False: Ionic bonds and nonpolar covalent bonds are considered the same kind of bond.
False
373
What is the relationship between electronegativity difference and bond polarity?
The greater the electronegativity difference, the more polar the bond.
374
What does the existence of polar bonds in a molecule indicate?
It does not necessarily mean that you have a polar molecule.
375
Give an example of a molecule that has polar bonds but is nonpolar.
Carbon dioxide (CO2)
376
What is the molecular shape of carbon dioxide according to the Lewis formula and VSEPR theory?
Linear
377
How is bond polarity typically represented?
As an arrow pointing from the positive side to the negative side of the bond.
378
What does the bond dipole represent?
The charge separation that occurs due to electronegativity differences between bonded atoms.
379
What do bond dipoles create when they are equal and opposite?
A zero total, resulting in a nonpolar molecule.
380
What is a nonpolar molecule?
A molecule where the bond dipoles balance each other, producing a molecular dipole of zero.
381
What is the molecular shape of water according to Lewis formula and VSEPR rules?
Angular
382
In a water molecule, do the bond dipoles balance each other?
No, they add together to produce a nonzero molecular dipole.
383
What charge does the oxygen atom have in a water molecule?
Partial negative charge
384
What charge do the hydrogen atoms have in a water molecule?
Partial positive charge
385
True or False: Water is a polar substance.
True
386
Fill in the blank: A _______ molecule is one where bond dipoles add to produce an overall dipole.
polar
387
What indicates that bond dipoles do not balance?
They produce a nonzero molecular dipole
## Footnote
This results in a polar molecule.
388
What explains the attraction of a stream of water to a positively charged strip?
The partial negative charge on the oxygen and partial positive charges on the hydrogens
## Footnote
This reflects the molecular dipole in water.
389
What is indicated by the shape of a molecule in relation to bond polarity?
The shape is as important as the bond polarity
## Footnote
This is illustrated by comparing carbon dioxide and water.
390
Is methane a polar or nonpolar substance?
Nonpolar substance
## Footnote
Despite having polar C-H bonds.
391
What explains why methane has no overall dipole?
The symmetrical arrangement of its bond dipoles
## Footnote
The tetrahedral shape leads to a vector sum of zero.
392
What type of molecules are always nonpolar?
Symmetrical molecules with one central atom
## Footnote
Examples include CCl4 and BF3.
393
Fill in the blank: The theory created by ______ consistently explains the polar or nonpolar nature of molecules.
VSEPR
## Footnote
This theory helps predict molecular geometry.
394
What does the stereochemical formula of methane show?
Four equal bond dipoles at tetrahedral angles
## Footnote
This leads to balanced dipoles.
395
True or False: The vector sum of bond dipoles in a symmetrical molecule is nonzero.
False
## Footnote
The vector sum is zero in symmetrical molecules.
396
What do bond dipoles create in a molecule?
A resultant molecular dipole
## Footnote
This is equal to the sum of the bond dipoles.
397
What is the nature of the ammonia molecule?
The ammonia molecule is polar
398
Why is the ammonia molecule considered polar?
It has bond dipoles that do not balance (cancel)
399
In what direction are the bond dipoles of the ammonia molecule angled?
Upward and sideways
400
How is the ammonia molecule symmetrical when viewed from above?
It is symmetrical sideways
401
How is the ammonia molecule asymmetric when viewed from the side?
It is not symmetrical vertically
402
What is the orientation of the resulting molecular dipole in an ammonia molecule?
Oriented vertically
403
What is the charge distribution on the ammonia molecule?
Slightly positive on the side with the hydrogens, slightly negative on the opposite side
404
What is the first step to predict the polarity of a molecule?
Draw a Lewis formula for the molecule.
405
What rules are used to determine the shape around each central atom?
VSEPR rules.
406
What is used to determine the polarity of each bond?
Electronegativities.
407
What do you add to determine if the final result is zero or nonzero?
Bond dipole vectors.
408
What indicates a nonpolar molecule?
Zero final result.
409
What indicates a polar molecule?
Nonzero final result.
410
Fill in the blank: To predict the polarity of a molecule, you must first _______.
Draw a Lewis formula for the molecule.
411
True or False: The shape around each central atom can be determined without considering electron pairs.
False.
412
What affects how a substance interacts with other substances?
The presence of polar molecules in the substance
## Footnote
Polar molecules influence solubility and interaction with other substances.
413
What does the phrase 'like dissolves like' refer to?
It refers to the principle that polar compounds dissolve in polar solvents and nonpolar compounds dissolve in nonpolar solvents
## Footnote
This principle is fundamental in chemistry for understanding solubility.
414
What are examples of nonpolar substances?
Greases and oils
## Footnote
Nonpolar substances do not mix well with polar substances like water.
415
Why is water not effective at dissolving oil or grease?
Because water is an extremely polar liquid and oils are nonpolar
## Footnote
This characteristic makes cleaning oily stains difficult.
416
What is a common use of greases and oils?
As protective coatings to repel water and prevent rust on metal parts
## Footnote
Aboriginal peoples used animal fat for waterproofing leather clothing.
417
How do modern silicone water repellents work?
They use synthetic molecules to repel water
## Footnote
This is similar to traditional methods of waterproofing.
418
What happens to oil droplets in the presence of detergent molecules?
The long nonpolar sections of detergent molecules dissolve in the oil droplet
## Footnote
This interaction helps to remove oil stains from fabrics.
419
What role does the polar end of detergent molecules play?
It helps form a polar layer around the oil droplet that attracts polar water molecules
## Footnote
This allows the oil droplet to be suspended in wash water.
420
Fill in the blank: '______ is not good at dissolving oil or grease.'
Water
## Footnote
Water's polarity limits its ability to interact with nonpolar substances.
421
True or False: Polar compounds are soluble in nonpolar solvents.
False
## Footnote
Polar compounds only dissolve in polar solvents.
422
What affects how a substance interacts with other substances?
The presence of polar molecules in the substance
## Footnote
Polar molecules influence solubility and interaction with other substances.
423
What does the phrase 'like dissolves like' refer to?
It refers to the principle that polar compounds dissolve in polar solvents and nonpolar compounds dissolve in nonpolar solvents
## Footnote
This principle is fundamental in chemistry for understanding solubility.
424
What are examples of nonpolar substances?
Greases and oils
## Footnote
Nonpolar substances do not mix well with polar substances like water.
425
Why is water not effective at dissolving oil or grease?
Because water is an extremely polar liquid and oils are nonpolar
## Footnote
This characteristic makes cleaning oily stains difficult.
426
What is a common use of greases and oils?
As protective coatings to repel water and prevent rust on metal parts
## Footnote
Aboriginal peoples used animal fat for waterproofing leather clothing.
427
How do modern silicone water repellents work?
They use synthetic molecules to repel water
## Footnote
This is similar to traditional methods of waterproofing.
428
What happens to oil droplets in the presence of detergent molecules?
The long nonpolar sections of detergent molecules dissolve in the oil droplet
## Footnote
This interaction helps to remove oil stains from fabrics.
429
What role does the polar end of detergent molecules play?
It helps form a polar layer around the oil droplet that attracts polar water molecules
## Footnote
This allows the oil droplet to be suspended in wash water.
430
Fill in the blank: '______ is not good at dissolving oil or grease.'
Water
## Footnote
Water's polarity limits its ability to interact with nonpolar substances.
431
True or False: Polar compounds are soluble in nonpolar solvents.
False
## Footnote
Polar compounds only dissolve in polar solvents.
432
What are intermolecular forces?
Forces of attraction and repulsion between molecules
## Footnote
Intermolecular forces differ from intramolecular forces, which refer to covalent bonds within a molecule.
433
What physical property is suggested to depend on intermolecular forces?
Wetting
## Footnote
Wetting is influenced by the ability of a material to interact with water molecules.
434
Why does cotton absorb water well?
It can form many intermolecular attractions with water molecules
## Footnote
This property makes cotton unsuitable for raincoats.
435
Why do rubber and plastic materials not absorb water?
There is little intermolecular attraction between water molecules and the molecules of rubber or plastic
## Footnote
This lack of attraction results in poor wetting properties.
436
What is a water repellent?
A coating that has little attraction to water molecules
## Footnote
Water repellents are used to treat materials like cotton to make them resistant to water.
437
True or False: Intermolecular forces are the same as intramolecular forces.
False
## Footnote
Intramolecular forces refer to forces within a molecule, while intermolecular forces are between different molecules.
438
Fill in the blank: The development of water repellents requires a good knowledge of _______.
intermolecular forces
## Footnote
Understanding these forces is crucial for creating effective water-repellent materials.
439
What are intermolecular forces?
Forces of attraction and repulsion between molecules
## Footnote
Intermolecular forces differ from intramolecular forces, which refer to covalent bonds within a molecule.
440
What physical property is suggested to depend on intermolecular forces?
Wetting
## Footnote
Wetting is influenced by the ability of a material to interact with water molecules.
441
Why does cotton absorb water well?
It can form many intermolecular attractions with water molecules
## Footnote
This property makes cotton unsuitable for raincoats.
442
Why do rubber and plastic materials not absorb water?
There is little intermolecular attraction between water molecules and the molecules of rubber or plastic
## Footnote
This lack of attraction results in poor wetting properties.
443
What is a water repellent?
A coating that has little attraction to water molecules
## Footnote
Water repellents are used to treat materials like cotton to make them resistant to water.
444
True or False: Intermolecular forces are the same as intramolecular forces.
False
## Footnote
Intramolecular forces refer to forces within a molecule, while intermolecular forces are between different molecules.
445
Fill in the blank: The development of water repellents requires a good knowledge of _______.
intermolecular forces
## Footnote
Understanding these forces is crucial for creating effective water-repellent materials.
446
What property allows trees to move water from the ground to the leaves?
Capillary action
## Footnote
Capillary action is a result of intermolecular forces that allow water to move through small spaces.
447
Who suggested the existence of van der Waals forces?
Johannes van der Waals
## Footnote
Van der Waals proposed that gases condense when cooled due to weak attractive forces between molecules.
448
What happens to gas molecules when molecular motion is slowed sufficiently?
They collect together and form a liquid
## Footnote
This phenomenon is indicative of the presence of intermolecular forces.
449
What is the relationship between intermolecular forces and covalent bonds?
Intermolecular forces are considerably weaker than covalent bonds
## Footnote
This is supported by experiments measuring bond energies.
450
What type of forces are often referred to as van der Waals forces?
Weak attractive forces between molecules
## Footnote
These forces can be a combination of various types of intermolecular forces.
451
What is an example of a substance with strong intermolecular forces?
Water
## Footnote
Water's intermolecular forces are among the strongest known, despite being weaker than covalent bonds.
452
Fill in the blank: Water molecules attract each other to maintain a _______ column of water.
continuous
## Footnote
This attraction is crucial for processes like capillary action.
453
What must water molecules do to facilitate capillary action in trees?
Attract the molecules in the walls of the tiny tubes
## Footnote
This attraction helps maintain the flow of water through the tree's structure.
454
What does it take less energy to do: overcome molecular forces in water or to break covalent bonds in water?
Overcome molecular forces in water
## Footnote
This indicates the relative strength of intermolecular forces compared to covalent bonds.
455
True or False: Van der Waals forces are the only type of intermolecular forces.
False
## Footnote
Van der Waals forces are a combination of many types of intermolecular forces.
456
What is the energy required to decompose water (H₂O) compared to the energy needed to overcome its intermolecular forces?
It takes much more energy to decompose water
## Footnote
This highlights the strength of covalent bonds compared to intermolecular forces.
457
What are intermolecular forces responsible for in molecular substances?
Intermolecular forces are responsible for the physical observations of molecular substances.
458
How many molecules are typically present in a visible sample of sucrose?
Trillions of trillions of molecules.
459
What structure do intermolecular forces help create in sucrose?
A crystalline solid structure.
460
Which solvent dissolves sugar extremely well?
Water.
461
Which solvent does not dissolve sugar well?
Alcohol.
462
What happens to sugar when heated to about 170°C?
The covalent bonds in the molecules start to break, leading to decomposition.
463
What is the term for the process of molecules separating completely from each other?
Vaporization or boiling.
464
What kind of reaction occurs when sugar is heated and the covalent bonds break?
A chemical reaction (decomposition) that creates totally new substances.
465
What physical properties of substances are affected by intermolecular forces?
Boiling point, rate of evaporation, and surface tension.
466
What is the approach taken to study intermolecular forces and their effects?
Comparing simple, similar substances and making qualitative comparisons.
467
True or False: Intermolecular forces are the only factors affecting physical properties.
False.
468
Fill in the blank: To understand the properties of substances, we need to look at various kinds of _______.
intermolecular forces.
469
What is the attraction between dipoles called?
Dipole-dipole force
## Footnote
Dipole-dipole forces are the attractions between oppositely charged sides of polar molecules.
470
What effect do dipole-dipole forces have on solvents?
They affect the ability of solvents to dissolve some solutes and not others
## Footnote
Dipole-dipole forces are among the weakest intermolecular forces but can significantly influence solubility.
471
Who suggested that the van der Waals force consists of two forces?
Fritz London
## Footnote
Fritz London proposed that the van der Waals force includes both dipole-dipole force and London force.
472
What is the London force also known as?
Dispersion force
## Footnote
The London force is responsible for the attraction between nonpolar molecules.
473
What causes momentary dipoles in molecules?
Movement of electrons
## Footnote
Momentary dipoles occur when the distribution of electrons in a molecule is not perfectly even.
474
What happens when momentary dipoles occur in adjacent molecules?
They result in overall attraction
## Footnote
This attraction is due to the temporary dipoles influencing each other.
475
How does the number of electrons in a molecule affect the London force?
More electrons lead to stronger London force
## Footnote
Larger molecules with more electrons can create more significant momentary dipoles.
476
True or False: London forces are present only between polar molecules.
False
## Footnote
London forces are present between all molecules, regardless of polarity.
477
Fill in the blank: The dipole-dipole force is considered to be among the _______ intermolecular forces.
weakest
## Footnote
Despite being weak, dipole-dipole forces can control important properties of substances.
478
What is the significance of London force in larger molecules?
The shape of larger molecules affects London force
## Footnote
The effective attraction from London forces is influenced by the spatial arrangement of electrons.
479
What is the attraction between dipoles called?
Dipole-dipole force
## Footnote
Dipole-dipole forces are the attractions between oppositely charged sides of polar molecules.
480
What effect do dipole-dipole forces have on solvents?
They affect the ability of solvents to dissolve some solutes and not others
## Footnote
Dipole-dipole forces are among the weakest intermolecular forces but can significantly influence solubility.
481
Who suggested that the van der Waals force consists of two forces?
Fritz London
## Footnote
Fritz London proposed that the van der Waals force includes both dipole-dipole force and London force.
482
What is the London force also known as?
Dispersion force
## Footnote
The London force is responsible for the attraction between nonpolar molecules.
483
What causes momentary dipoles in molecules?
Movement of electrons
## Footnote
Momentary dipoles occur when the distribution of electrons in a molecule is not perfectly even.
484
What happens when momentary dipoles occur in adjacent molecules?
They result in overall attraction
## Footnote
This attraction is due to the temporary dipoles influencing each other.
485
How does the number of electrons in a molecule affect the London force?
More electrons lead to stronger London force
## Footnote
Larger molecules with more electrons can create more significant momentary dipoles.
486
True or False: London forces are present only between polar molecules.
False
## Footnote
London forces are present between all molecules, regardless of polarity.
487
Fill in the blank: The dipole-dipole force is considered to be among the _______ intermolecular forces.
weakest
## Footnote
Despite being weak, dipole-dipole forces can control important properties of substances.
488
What is the significance of London force in larger molecules?
The shape of larger molecules affects London force
## Footnote
The effective attraction from London forces is influenced by the spatial arrangement of electrons.
489
What is the dipole-dipole force?
The dipole-dipole force is due to the simultaneous attraction between any one dipole and all surrounding dipoles.
490
What factors influence the strength of the dipole-dipole force?
The strength of the dipole-dipole force is dependent on the overall polarity of the molecule.
491
What causes the London force?
The London force is due to the simultaneous attraction between a momentary dipole in a molecule and the momentary dipoles in the surrounding molecules.
492
What factors affect the strength of the London force?
The strength of the London force is directly related to the number of electrons in the molecule and inversely related to the distance between the molecules.
493
How can dipole-dipole and London forces be used?
They can be used to predict boiling points of compounds.
494
What determines the boiling points of Group 4 hydrogen compounds?
The boiling points can be determined based on the number of electrons and protons in the compounds.
495
What is the significance of VSEPR and molecular shape in predicting polarity?
Molecules can be predicted to be nonpolar based on their four equivalent bonds and their tetrahedral shape.
496
True or False: The strength of the London force increases with the distance between molecules.
False
497
Fill in the blank: The covalent bond is explained by simultaneous _______ of a pair of negative electrons by two positive nuclei.
attraction
498
What is an ionic bond?
An ionic bond is the simultaneous attraction of oppositely charged ions.
499
What are scientists always seeking in their research?
Scientists are always seeking a synthesis of different explanations.
500
What is the boiling point of methane (CH4)?
−162 °C
## Footnote
Boiling point indicates the temperature at which a substance transitions from liquid to gas.
501
What is the boiling point of ethane (C2H6)?
−89 °C
## Footnote
Ethane is a two-carbon alkane.
502
What is the boiling point of propane (C3H8)?
−42 °C
## Footnote
Propane is a three-carbon alkane.
503
What is the boiling point of butane (C4H10)?
−1 °C
## Footnote
Butane is a four-carbon alkane.
504
According to intermolecular force theory, which hydrocarbon has the highest boiling point?
Butane
## Footnote
Butane has the most attractive London forces due to having the greatest number of electrons.
505
What are isoelectronic molecules?
Molecules with the same number of electrons
## Footnote
Isoelectronic molecules help in studying intermolecular forces.
506
What is the relationship between molecular shape and London forces in isoelectronic molecules?
Similar shapes lead to similar strengths of London forces
## Footnote
This is important for predicting boiling points.
507
If one of two isoelectronic substances is polar and the other is nonpolar, which will have a higher boiling point?
The polar molecule
## Footnote
Polarity increases intermolecular attraction, raising boiling points.
508
What is the boiling point of bromine?
−7.2 °C
## Footnote
Bromine is a diatomic molecule with significant intermolecular forces.
509
What is the boiling point of dichloromethane?
39.6 °C
## Footnote
Dichloromethane is a polar molecule with higher boiling point due to dipole-dipole interactions.
510
Fill in the blank: According to empirical rules, butane has the most attractive _______ due to its number of electrons.
London forces
## Footnote
London forces are a type of van der Waals force due to temporary dipoles.
511
What is the relationship between isoelectronic molecules of similar shape and London forces?
Isoelectronic molecules of similar shape have approximately the same strength of London force between them.
512
How does molecular polarity affect dipole-dipole forces and boiling points?
The more polar the molecule, the stronger the dipole-dipole force and, therefore, the higher the boiling point.
513
What is the effect of the number of electrons per molecule on London forces?
The greater the number of electrons per molecule, the stronger the London force and, therefore, the higher the boiling point.
514
When can you predict the relative boiling points of two substances based on London and dipole-dipole forces?
You can explain and predict the relative boiling points of two substances if the London force is the same, but the dipole-dipole force is different.
515
What happens when the dipole force is the same but the London force is different?
You can explain and predict the relative boiling points of two substances if the dipole force is the same, but the London force is different.
516
What can you conclude if both the London force and dipole-dipole force are greater for one substance?
Both the London force and the dipole-dipole force are greater for one substance, leading to a higher boiling point.
517
True or False: You can predict the boiling points of two substances if one has a stronger dipole-dipole force and the other has a stronger London force.
False.
518
Fill in the blank: The boiling point is affected by both _______ and dipole-dipole forces.
[London forces]
519
What factors must be equal to predict relative boiling points based on London forces?
The London force must be the same.
