Chapter 2: Chemical Bonding and Lewis Structures Flashcards
(38 cards)
1
Q
compounds (2)
A
- chemicals that are combinations of 2 or more different elements in defined properties
- do not have overall charges (“charge neutral”)
2
Q
ions (2)
A
- species possessing an overall negative charge or overall positive charge
- cannot be isolated, (they are insoluble) in their condensed phases (liquid, solid) without ion of opposite charge present to balance the charge to form a net-neutral compound
3
Q
anion
A
- ions carrying an overall negative charge
4
Q
cation
A
- ions carrying an overall positive charge
5
Q
simple ions
A
- ions that contain a single atom
6
Q
complex ions (2)
A
- ions that contain multiple atoms
- aka polyatomic atoms or molecular atoms
7
Q
purpose of forming bonds
A
- elements achieve a lower overall energy than they would in their free elemental form
8
Q
ionic bonds
A
- occur when oppositely charged ions are help together by electrostatic forces
9
Q
covalent bonds
A
- occur when atoms are held together by mutual attraction of a pair (or pairs) of electrons to the nuclei in adjacent atoms, the electrons are “shared” between atoms
10
Q
metallic bonds (2)
A
- occur when electrons are shared between many atoms simultaneously and are free to “flow” between atoms
- in elemental metals or metallic alloys (mixture of two or more elemental metals), this bond is the most important
11
Q
electronegativity (2)
A
- tendency of an atom in a molecule to attract electrons to itself
- cannot be discussed unless it is apart of a molecule or molecular ion
12
Q
polar covalent bonds
A
- electrons are polarized towards the atom with greater electronegativity, so the electrons are shared unequally
13
Q
bond polarity (2)
A
- measured by the subtraction of the lesser electronegativity from the greater electronegativity
- bonds with high differences in electronegativity can be considered to be ionic
14
Q
ionic compounds (4)
A
- commonly referred to as salts
- consist of ions held together with electrostatic forces
- when melted, cations and anions move past each other freely and resulting liquid conducts electricity
- can carry a charge from one place to another, motion of charged ions result in an electric current
15
Q
can covalent compounds conduct electricity in a liquid state?
A
- they do not conduct electricity as there are no ions present after melting, covalent bonds remain intact during phase changes
16
Q
how do the alkali metals (group 1) and alkaline earth metals react (group 2) in ionic compounds
A
- group 1 metals are found as M+ ions in ionic compounds
- group 2 metals are found as M2+ ions in ionic compounds
17
Q
redox reaction (2)
A
- total number of electrons lost must be equal to the total number of electrons gained
- in a reaction between an alkali metal atom and a halogen atom the electron is formally transferred from the alkali to the halogen: the alkali metal is oxidized and the halogen is reduced
18
Q
covalent bond (2)
A
- exists when a pair of electrons is shared between 2 atoms
- pair of electrons is called a bond pair, valence electrons that do not participate are called lone pair
19
Q
bond order
A
- number of bond pairs between two atoms
20
Q
bond length
A
- distance between 2 nuclei participating in a bond
21
Q
bond dissociation energy
A
- determines strength of a bond, experimental value describing how much energy needs to be added to break a particular bond
22
Q
describe the trend between bond order, length and dissociation energy
A
- smaller bond order: larger bond length and smaller dissociation energy
23
Q
bond dipole (2)
A
- result of electrons being polarized towards the atom with greater electronegativity
- one atom will have a partial positive charge and the other will have a partial negative charge
24
Q
what symbol is used to indicate a bond dipole
A
- arrow with a crossed tail is used to indicate the direction of a bond dipole (points towards excess negative charge)
25
how do you measure percent character of a bond
- ratio of the actual bond dipole to the bond dipole if the bond was purely ionic
26
octet rule
- atom satisfy this rule is they have 8 valence electrons, achieved by forming covalent bonds
27
how do you determine whether an atom has a complete octet?
1. count the lone pair electrons on the atom
2. count all bonding electrons (twice the number of bonds to the atom)
3. octet rule is satisfied if #1 and #2 have a complete octet
28
"electron deficient" compounds (2)
- group 13 elements only have 3 valence electrons in their outer shell and can achieve a maximum of six valence electrons
- these compounds do not have to conform to octet rule as they are unable to achieve a complete octet
29
hypervalent species (3)
- species containing elements in the third or later periods of the p-block may have more than an octet of electrons
- central atom has an expanded octet
- "central atom with more electrons in its valence shell then predicted in the octet rule"
30
free radicals
- species that contain unpaired electrons
31
formal charge
- determined by imagining bonding electrons are shared exactly equally between atoms and occurs when bonded atom has a greater or fewer number of electrons than its free form
32
what is the procedure for drawing valid lewis structures for species with one central atom
1. arrange atom symbols
2. add valence electrons
3. draw bonds
4. rearrange electrons for octet and check octet rule
5. label formal charges
6. check electron count
33
when do resonance structures exist? (2)
- when two are more Lewis structures can represent the arrangement of electrons in the same molecule or molecular ion
- positions and connectivity of the atomic nuclei are identical
34
valid resonance structures
- any structure where the octet rule is satisfied on all atoms (other than known exceptions)
35
best resonance structures
- a structure that has minimal formal charges and has negative formal charges on more electronegative elements
36
chemically reasonable resonance structure (2)
- any valid resonance structure where the magnitudes of the formal charges are small
- represent bonding that is typical of various elements
37
isomers
- chemical species that have the same molecular formula, but a different arrangement of atoms, not to be confused with resonance structures
38
acid-base theory
- the acid is the proton (H+) donor and the base is the proton acceptor
