Topic 1- Key Concepts Of Chemistry Flashcards
(189 cards)
1
Q
How many different types of elements are there that humans have discovered ?
A
118
2
Q
What are atoms ?
A
the smallest pieces of an element that can exist
3
Q
What is Fe ?
A
Iron
4
Q
What is the element Co ?
A
Cobalt
5
Q
What is the element oxygen ?
A
O
6
Q
Atoms of different elements can be combined together to create what ?
A
compounds
7
Q
How are the formula of compounds made ?
A
By combining the chemical symbols of the elements that combine to make them
8
Q
Combining different atoms creates what ?
A
different compounds
9
Q
What does every compound contain ?
A
at least 2 different elements.
10
Q
Combining sodium (Na) atoms and oxygen (O) atoms produces what ?
A
sodium oxide
11
Q
What is the formula of sodium oxide ?
A
Na2O
12
Q
What are the key features of a chemical reaction ?
A
Compounds are broken up or formed
At least 1 new substance is formed
Measurable energy change
No atoms are created or destroyed
13
Q
Where are the reactants in an equation ?
A
left hand side
14
Q
Where are the products of an equation ?
A
Right hand side
15
Q
Whats the word equation for sodium + oxygen ?
A
sodium + oxygen → sodium oxide
16
Q
What is the balanced symbol equation for sodium oxide ?
A
4Na + O2 → 2Na2O
17
Q
In 1803 what did john Dalton suggest ?
A
first suggested that all matter is made of atoms and that atoms cannot be split.
18
Q
How did scientists improve daltons original model of an atom .
A
with the discovery of sub-atomic particles.
19
Q
In 1897, an English physicist called what discovered what ?
A
J. J. Thomson discovered electrons
20
Q
How did JJ Thomson model the atom ?
A
as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants) mixed in with the ‘dough’
21
Q
In 1909 what did Ernest Rurherford discover ?
A
that alpha particles could bounce back off atoms.
22
Q
What did Ernest Rurherford conclude ?
A
an atom’s mass is concentrated in the atom’s centre. This was called the “nucleus” and it contained positively charged particles called protons.
23
Q
What did Niels Bohr discover ?
A
discovered that electrons orbit (fly around) the nucleus at fixed distances
24
Q
In 1932, what did James Chadwick discover ?
A
some particles in the nucleus have no charge at all. He called them neutrons.
25
What are the three sub-atomic particles ?
Proton
Electron
Neutrons
26
Where are protons found ?
They are found in the nucleus.
27
What is the relative charge of protons ?
Protons have a relative charge of +1.
28
What is the relative atomic mass of protons ?
1
29
An elements atomic number is what ?
An element’s atomic number is the number of protons it possesses.
30
All atoms of the same element have what ?
an identical number of protons.
31
What is the relative charge of an electron ?
Electrons have a relative charge of -1.
32
Where are electrons found ?
in fixed orbits around the nucleus.
33
In any atom the total number if negative electroms equals what ?
In any atom, the total number of negative electrons equals the number of positive protons, meaning atoms have no overall electric charge.
34
What is the relative atomic mass of electrons ?
1/2,000, which we approximate to be 0.
35
What is the relative charge of neutrons ?
Neutrons have a relative charge of 0 - they are neutral.
36
Where are neutrons found ?
Like protons, they are found in the nucleus.
37
What is the relative atomic mass of neutrons ?
1
38
What is the overall charge of the nucleus of an atom ?
Positive
39
What is an atom made up of ?
a positively charged nucleus surrounded by negatively charged electrons.
40
Whatnis the radius of an atom ?
radius of atoms is aproximately 0.1 nanometres, or 1x10-10 m.
About 5 million hydrogen atoms could fit into a pin head.
41
How many times smaller is the nucleus of an atom then the whole atom ?
The nucleus of an atom is 10,000 times smaller than the atom.
42
Where is Most of an atom's mass concentrated ?
in the nucleus.
43
What is relative mass of an atom = to ?
Relative mass = number of protons + number of neutrons.
44
What is atomic number ?
is the number of protons in the atom
45
When looking at an atom on the periodic table how do we know the mass number and the atomic number ?
```
Mass number (top)
Atomic number (bottom)
```
46
What is the mass number and atomic number of carbon ?
```
Mass number (top) = 12
Atomic number (bottom) = 6
```
47
What is the mass number and atomic number of sodium ?
```
Mass number (top) = 23.
Atomic number (bottom) = 11.
```
48
Magnesium (Mg) has an atomic number of 12. How many protons and electrons does a neutral Mg atom have?
12 protons and 12 electrons
49
What are isotopes ?
Isotopes are forms of an element that have the same number of protons, but a different number of neutrons.
50
What are hydrogens 3 isotopes ?
Protium
Deuterium
Tritium
51
What is protium ?
Protium is a hydrogen atom with 1 proton and 0 neutrons.
| 99.98% of hydrogen atoms are protium.
52
What is protium used for ?
It is used in hydrogen fuel cells and the production of plastics.
53
What is deuterium ?
Deuterium is a hydrogen atom with 1 proton and 1 neutron.
| Around 0.02% of hydrogen atoms are deuterium.
54
What is deuterium used for ?
It is used in nuclear fusion
55
What is tritium ?
Tritium is a hydrogen atom with 1 proton and 2 neutrons.
| It is very rare.
56
What is tritium used for ?
It is used in thermonuclear fusion weapons.
57
How many protons do hydrogen atoms contain?
1
58
Whats a nuclide ?
A nuclide is a type of isotope.
A nuclide refers to a specific nucleus that contains a certain number of protons and neutrons.
59
Fact about nuclides
A carbon nuclide with 6 protons and 6 neutrons is different to a carbon nuclide with 6 protons and 7 neutrons. However, both are isotopes of carbon.
60
Why do isotopes have the same properties?
Same number of electrons on their outer shell
61
How can we work out the realative atomic mass of chlorine ?
Relative atomic mass - chlorine
Chlorine can exist as 2 isotopes, 35Cl and 37Cl.
75% of chlorine is 35Cl
25% of chlorine is 37Cl
You can work out that the relative atomic mass (Ar) of chlorine is 35.5 using this information.
Ar = (0.75 x 35) + (0.25 x 37) = 35.5
62
What was rutherfords model called ?
Rutherford's model was called the nuclear model
63
The relative atomic mass (Ar) is what ?
the average mass of all of the isotopes of an element.
| It takes into account how often each isotope is found (the isotope abundance).
64
What is the equation for relative atomic mass ?
(Isotope abundance x isotope mass number)
——————- ——- - — ——————————
Isotope abundance
65
Calculate the relative atomic mass of uranium using these isotopic abundances (you will need a calculator to check):
238U - 50%
235U - 20%
234U - 30%
Remember the equation for relative atomic mass
RAM = Σ (isotope abundance x isotope mass number) / 100
Substitute the values in
RAM = (50 x 238) + (20 x 235) + (30 x 234) ÷ 100
Work out the brackets
RAM = (11,900 + 4700 + 7020) ÷ 100
Work out the answer
RAM = 236.2
66
Why is the periodic table ‘periodic’ ?
because elements with similar properties occur at regular intervals, i.e. periodically.
Therefore, the rows of the periodic table are called periods
67
Elements in the same column have the same number of what ?
Elements in the same column have the same number of electrons in their outer shell (the highest energy level).
Columns are called groups, and the group number equals the number of electrons an atom of that element has in its outer shell.
68
All elements in a column have the same number of electrons in their outer shell.
What does this mean ?
they have similar chemical properties.
This means they will all react in similar ways.
69
Every time you move an element to the right, what happens ?
the proton number increases by 1.
70
Who was john newlands ?
John Newlands was the first chemist to devise a periodic table.
71
How did john newlands oreder his periodic table ?
His periodic table was ordered by the weight of the element.
However, the table was incomplete, and some elements were placed in inappropriate groups.
72
What did Dmitri Mendeleev realise ?
Dmitri Mendeleev realised that there may be undiscovered elements.
73
How did Dmitri Mendeleev change Newlands table ?
He added gaps to Newlands’ table to account for undiscovered elements.
He even predicted the properties and masses of these undiscovered elements!
74
What discovery has shown that Mendeleev ordered elements exactly by atomic number (number of protons) ?
The discovery of protons and isotopes
Therefore, the modern periodic table looks very similar to Mendeleev's (except the gaps are filled).
75
Name the 2 scientists that were key influencers of the modern periodic table?
John Newlands
Dimitri Mendeleev
76
What is the atomic number?
Number of protons in an atoms nucleus
77
Where are metals found on the periodic table ?
Metals are found on the left of the periodic table because they have few electrons in their outer shell.
78
When metals react, what happens ?
When metals react, they lose 1 or more of these negatively charged electrons to form positively charged ions.
79
What are the properties of metals ?
Metals have high melting and boiling points.
Metals are good conductors of heat and electricity.
Metals are all solids (except for mercury) at room temperature.
80
Where are non metals found on the periodic table ?
Non-metals are found on the right of the periodic table because they have many electrons in their outer shell.
81
When non-metals react, what happens ?
Gain electrons to form negatively charged ions.
Or share electrons to form neutral molecules.
82
What are the properties of non-metals ?
Non-metals have lower melting and boiling points than metals.
Non-metals are often found as gases.
Non-metals generally do NOT conduct heat or electricity.
83
Electrons have fixed positions in atoms called what ?
shells or energy levels.
These shells (or energy levels) go around the atom's nucleus
84
Electrons fill an atom's shells in order of what .
increasing energy
85
The closer a shell is to the nucleus, the what ?
the lower its energy level
so the first shell that is filled is the closest to the nucleus.
86
Electron configuration tells us what ?
Electron configuration tells us how an atom's electrons are organised.
The inner shell (closest to the nucleus) can have a maximum of 2 electrons and the next two shells can have a maximum of 8 electrons.
Any extra electrons are then put into a fourth shell.
87
Calcium atoms have 20 electrons and so whats electron configuration ?
2, 8, 8, 2.
88
Which group of elements form DIATOMIC MOLECULES and become LESS REACTIVE as you move down the group?
Group 7
89
What can Dot-and-cross diagrams show ?
electrons being transferred and ions being formed.
Dots represent electrons from 1 atom and crosses represent electrons from the other atom.
Square brackets and a charge (e.g. 2+) represent ions.
90
Barium (Ba) is in group 2 and chlorine (Cl) is in group 7. In the dot-and-cross diagram for barium chloride, so how how many Barium ions and chlorine ions would there be ?
there would be 1 barium ion, and 2 chloride ions.
91
Sodium is in group 1 and oxygen is in group 6. In the dot-and-cross diagram for sodium oxide, how many sodium ions would there be?
2
92
When an atom gains or loses electrons, the nucleus does not change. What does this mean for the atomic mass and atomic number ?
This means the atomic mass and the atomic number stay the same.
93
Whats a cation ?
Positive ion
94
If an ion is positive it has fewer electrons then what ?
If an ion is positive, it has fewer electrons than protons.
95
A 1+ charge means what ?
| A 2+ charge means what ?
A 1+ charge means 1 less electron than proton (e.g. Na+).
| A 2+ charge means 2 less electrons than protons (Ca2+).
96
Whats anion ?
Negative ion
97
If an ion is negative, it has more electrons than what ?
Protons
98
A 1- charge means 1 what ?
| A 2- charge means 2 what ?
A 1- charge means 1 more electron than proton (e.g. Cl-).
| A 2- charge means 2 more electrons than protons (O2-).
99
How many more protons than electrons does an Na+ ion have ?
1
100
What happens in ionic bonding ?
In ionic bonding, a metal atom transfers electrons to a non-metal atom, allowing both of them (the metal and non-metal) to have a full outer electron shell
101
Group 1 metals always lose 1 electron to form what ?
positive ions with a charge of +1.
E.g. a sodium atom (Na), with the electronic structure (2,8,1), loses its outer electron when forming an ion to make Na+.
102
Group 2 metals always lose 2 electrons to form what ?
doubly positive ions.
E.g. a magnesium atom (Mg), with the electronic structure (2,8,2), loses both its outer electrons when forming an ion to make Mg2+.
103
Non-metal atoms always gain electrons to form (become) what ?
negative ions.
E.g. a fluorine atom (F), with the electronic structure (2,7), will gain an electron when forming an ion to make F-.
104
Why are noble gases unreactive ?
Noble gases already have a full outer shell.
| Noble gases are unreactive and don't normally form ionic bonds with other elements.
105
Complete the sentence
The _____ number in the periodic table tells you the number of electrons in an atom’s outer electron shell.
The group number in the periodic table tells you the number of electrons in an atom’s outer electron shell.
106
What are ions ?
Ions are particles that have a charge.
107
How are ions created ?
Ions are created when an atom or molecule gains or loses electrons.
108
Complete the sentence
Gaining electrons creates a __________ charged ion; losing electrons creates a __________ charged ion
Gaining electrons creates a negatively charged ion; losing electrons creates a positively charged ion
109
How are positive ions created ?
when an atom or molecule loses electrons.
110
What are positive ions often called ?
Cations
111
What can easily lose electrons to become positively charged ions (cations) ?
The metals in Group 1 and 2 can easily lose electrons to become positively charged ions.
112
How are negative ions created ?
when an atom or molecule gains electrons.
113
What are negative ions called ?
Anions
114
What are most likely to gain electrons to fill up their electron shell and become negatively charged ?
The non-metals in Group 7 are most likely to gain electrons to fill up their electron shell and become negatively charged.
115
What are the two ways ions can be made up ?
1 atom (e.g. F-).
Combinations of atoms with an overall charge (e.g. SO4^2-).
116
How can we predict the charge of atoms ?
from the periodic table based on the group number
117
What is the charge of An ionic compound formula ?
no overall charge
118
Ionic compounds made from 2 different elements end in what ?
-ide
119
Ionic compounds made from 3 or more different elements end in what ?
-ate
120
Potassium forms K+ and oxygen forms O2-.
We need 2 potassium ions (K+) to cancel out the 2- charge to the oxygen.
So what is the formula ?
Therefore, the formula becomes K2O.
121
When there are multiple groups of atoms, we must use what ?
Brackets
122
Calcium forms a Ca2+ ion, and a nitrate ion that has the formula NO3-.
We need two nitrate ions to cancel out the 2+ charge to the calcium.
Therefore, calcium nitrate has a formula of what ?
Ca(NO3)2.
123
Calcium nitrate has the formula Ca(NO3)2. Calcium forms a Ca2+ ion. What is the charge on a nitrate ion?
To make calcium nitrate, we need 2 units of (NO3) for 1 unit of Ca2+.
So 1 nitrate ion must have a charge of −1 and have the formula NO3-.
124
What type of structure are ionic lattices?
Giant structures
125
How are covalent bomds formed ?
Covalent bonds are formed when 2 non-metal atoms share pairs of electrons.
126
Why are covalent bomds strong ?
Covalent bonds are strong because the shared electrons are attracted to the nucleus of both atoms
127
What can Covalently bonded substances be ?
Small molecules - water
Large molecules - polymers such as polyester and silk
Giant covalent structures - diamond
128
What can be used to represent covalent bonds and show the sharing of electron pairs ?
Dot-and-cross diagrams
129
```
Each chlorine (Cl) atom begins with 7 electrons in its outer shell.
By sharing 1 pair of electrons in a single covalent bond, each Cl atom obtains what ?
```
a full outer shell with 8 electrons
130
Because oxygen has 6 electrons in its outer shell, it needs to have 2 extra electrons shared with it to get a full outer electron shell.
To do this, it forms a single covalent bond with what ?
2 hydrogen atoms.
131
Fact
The earlier examples show single covalent bonds (1 shared pair of electrons between atoms), but it is also possible to form double (2 shared pairs) and even triple covalent bonds (3 shared pairs).
Double and triple bonds are normally stronger and require more energy to break.
132
Each oxygen needs 2 electrons to get a full outer shell.
Therefore, each oxygen atom shares 2 electrons with the other, leaving 2 pairs of electrons in the shared space between the atoms.
What is this an example of ?
This is an example of a double covalent bond.
133
Nitrogen atoms have 5 electrons in their outer shell.
What type of bond forms between 2 nitrogen atoms?
Triple covalent bond
134
When compared with single covalent bonds, double and triple covalent bonds...
Require more energy to break
| Are stronger
135
When nitrogen reacts with hydrogen to form ammonia, how many hydrogen atoms will bond to each nitrogen atom?
3
136
Which diatomic element has a triple covalent bond?
Nitrogen
137
Ionic compounds form giant structures called what ?
Ionic compounds form giant structures called ionic lattices
138
What are ionic lattices held together by ?
strong electrostatic forces of attraction between positive and negative ions.
139
What are the strong electrostatic forces of attraction between positive and negative ions called ?
These forces are called ionic bonds.
140
The lattice structure of ionic compounds give them what properties ?
High melting and boiling points
Dont conduct electricity if solid
Conduct electricity if liquid or in solution
141
Why do ionic compounds in a lattice structure have a high melting and boiling point ?
To break ionic bonds, significant energy is needed to overcome the electrostatic forces between the ions and electrons in the lattice.
Because of this, the melting and boiling points of ionic compounds is high.
142
Why dont ionic compounds in a lattice structure conduct electricity if solid ?
When solid, the ions in the lattice are fixed in place.
| This means that charges cannot flow, so electricity cannot be conducted.
143
Why do ionic compunds in a lattice structure Conduct electricity if liquid or in solution
When molten, or dissolved in water, the ions in the lattice can move freely.
Because of this, charge can flow and electricity can be conducted.
144
What are intramolecukar foreces ?
Intramolecular forces are forces within molecules.
145
What are small covalent molecukes held together by ?
Small covalent molecules are held together by strong intramolecular forces called covalent bonds
146
Lots of small covalent molecules can be held together by what ?
Lots of small covalent molecules can be held together by intermolecular forces
But these intermolecular forces are weak and easy to break. This means small covalent molecules have low melting and boiling points (they're often liquids or gases at room temperature).
147
How would you describe the intramolecular bonds and intermolecular forces associated with small molecules ?
Intramolecular covalent bonds are strong
Intermolecular forces are weak
148
What does the size of a molecule affect ?
The size of a molecule affects the overall strength of intermolecular forces.
149
What does the strength of intermolecular affect ?
The strength of intermolecular forces affects the properties of a molecule
150
Why cant small molecules comduct electricity ?
Small molecules don't contain delocalised electrons. Because of this, they cannot conduct electricity.
151
Small molecules have weak intermolecular forces what does this mean ?
This means that they have low melting and boiling points.
| Because of this, they are often liquids or gases at room temperature.
152
How is Chlorine an example of a small molecule ?
Cl2 (the diatomic molecule of chlorine) is a small molecule with weak intermolecular forces between its molecules.
It is a gas at room temperature
153
Bigger molecules attract other molecules with what ?
Bigger molecules attract other molecules with stronger intermolecular forces.
This means that they have higher melting and boiling points than small molecules.
154
Why cant bigger molecules conduct electricity ?
Don't contain delocalised electrons, and so can't conduct electricity.
155
How is Sucrose an example of a bigger molecule
Sucrose is made of 45 atoms and has the formula C12H22O11.
Although it is a simple molecule, its size means that its intermolecular forces are strong enough for it to be solid at room temperature.
156
Why are small covalent molecules liquids or gases at room temperature?
When small molecules melt or boil, it's the weak intermolecular forces that break.
Since these intermolecular forces are weak and break easily, simple covalent molecules have very low melting and boiling points.
Therefore, they exist as liquid and gases at room temperature.
157
What do Some non-metals form when atoms are joined together by covalent bonds ?
giant covalent structures
158
What are the properties of giant covalent structures ?
No specific formula
Very high melting point
1 large molecule
159
Why dont Giant covalent structures have a specific formula ?
Giant covalent structures don't have a specific formula because the structure can be any size.
160
Why do giant covalent structures have a very high melting point ?
The strong covalent bonds between atoms make them solids at room temperature.
High temperatures and significant energy are required to break the structure's covalent bonds
161
In giant covalent structures why is there no intermolecular forces ?
Giant covalent structures exist as 1 large structure or molecule.
There are no intermolecular forces because there is only 1 molecule
162
What are the ways of representing covalent bonds ?
As lines between atoms
Dot-and-cross with shells - Dots represent the outer shell electrons of atoms of 1 element.
Crosses represent the outer shell electrons of atoms of the other element.
Dot-and-cross without shells - Dots represent the outer shell electrons of atoms of 1 element.
Crosses represent the outer shell electrons of atoms of the other element.
Ball-and-stick - Balls represent atoms , Sticks represent bonds between the atoms.
163
Whats a limitation of dot and cross diagrams ?
A limitation of this method is that it shows electrons differently for each atom, when they are actually exactly the same.
164
Whats a limitation of ball and stick diagrams ?
A limitation of this method is that atoms are much closer together than the diagram shows.
165
What are examples of 4 different types of covalent molecules ?
Giant covalent structures - Graphite and Diamond
Polymers - Poly(ethene) and Poly(propene)
Large covalent molecules - Long chain alkanes and Sucrose
Small covalent molecules - Oxygen and Carbon monoxide
166
What is diamond an allotrope of ?
Diamond is an allotrope (form) of carbon
167
What are the properties of diamond ?
High melting point
Doesnt conduct electricity
Contains covalent bonds
Very hard
168
Why does diamond have such a high melting point ?
A lot of energy is needed to break strong covalent bonds.
Diamond has lots of strong covalent bonds. This means that it has a high melting point.
169
Why doesnt diamond conduct electricity ?
Diamond does not conduct electricity because there are no delocalised electrons in the diamond structure.
170
Each carbon atom in diamond is bonded to 4 other carbon atoms by strong covalent bonds.
What doesnthis create ?
This creates a giant covalent structure
171
Why is diamond so hard ?
There are lots of strong covalent bonds in diamond. This makes it very hard.
172
Because diamond is hard, what is it used for ?
Because diamond is hard, it is used as a cutting tool to cut other materials
173
How many other carbon atoms is each carbon atom in diamond bonded to?
4
174
What is graphite an allotrope of ?
Graphite is an allotrope (form) of carbon
175
What are the properties of graphite ?
Graphite is soft
Graphite conducts electricity
Contains covalent bonds
176
Why is graphite soft ?
The carbon atoms form layers of hexagonal (6-sided) rings, with weak intermolecular forces keeping the layers together.
The layers can easily slide over one another, so graphite is very soft.
This makes graphite useful as a lubricant and as pencil ‘lead’.
177
How can graphite conduct electricity ?
Each carbon atom forms 3 bonds.
This means that there is 1 delocalised electron from every carbon atom.
This electron can move freely, so graphite is a good electrical conductor
178
Each carbon atom in graphite is bonded to 3 other carbon atoms by strong covalent bonds.
What does this create ?
This creates a giant covalent structure.
179
Describe the structure of graphite ?
Graphite is 1 of several allotropes (forms) of carbon. The weak intermolecular forces in graphite allow the layers to easily slide over one another. There is 1 delocalised electron from every carbon atom, which allows charge to flow and makes graphite a good conductor of electricity.
180
What are Fullerenes ?
Fullerenes are molecules of carbon atoms that take up hollow structures
181
What is the structure of fullerenes ?
Their structure is usually carbon atoms arranged in hexagonal (6-sided) rings, but pentagonal (5-sided) and heptagonal (7-sided) carbon rings can also be found.
182
What was the first fullerene to be discovered ?
Buckminsterfullerene was the first to fullerene that was discovered
183
What is the shape and formula of Buckminsterfullerene?
Buckminsterfullerene has a spherical shape and its formula is C60.
184
Why is Buckminsterfullerene technically a simple molecule ?
Buckminsterfullerene is technically a simple molecule because of its fixed size.
185
What are the uses of Spherical fullerenes ?
Generally speaking, spherical fullerenes come in a wide range of sizes, and their common uses include:
Catalysts.
Lubricants.
As vehicles for transporting drugs into our bodies.
186
What are the properties of Cylindrical fullerenes ?
Cylindrical fullerenes - shape
Carbon nanotubes are cylindrical fullerenes.
They are often called molecular wires because they have a tiny diameter but can be incredibly long.
Conduct electricity
Strong
Small diameter
187
Why are Cylindrical fullerenes so strong ?
Because of the strong covalent bonds between carbon atoms, nanotubes are exceptionally strong for their size
188
What are the uses of Cylindrical fullerenes ?
The strength and electrical conductivity of nanotubes make them useful:
In electronics.
In nanotechnology.
For strengthening materials (e.g. tennis racket frames).
189
The structure of fullerenes is based primarily on rings of how many carbon atoms?
6
