—Paper 1 Chemistry AS-Level AQA—
Sodium fluoride contains sodium ions (Na+) and Fluoride ions (F-). Na+ and F- have the same
electron configuration. Explain why a fluoride ion is larger than a sodium ion.
[2 marks] Jun2019/1
- The fluoride ion has two fewer protons than the sodium ion / lower nuclear charge.
- Weaker attraction between nucleus and outer/valence electrons.
Explain in terms of structure and bonding, why the melting point of sodium fluoride is high.
[2 marks] Jun2019/1
- Electrostatic forces of attraction between oppositely charged ions Na+/F-
- A large amount of energy is needed to break/overcome these forces.
Describe how the molecules are ionised using electrospray ionisation. [3 marks] Jun2019/1
- The sample is dissolved in a volatile solvent.
- Injected through needle/nozzle capillary at high voltage/positively charged.
- Each molecule particle gains a proton/H+ ion.
The first ionisation energies of the elements in period 2 change as the atomic number increases.
Explain the pattern in the first ionisation energies of the elements from lithium to neon.
[ 6 marks] Jun2019/1
(Stage 1) general trend Li→Ne:
- 1st ionisation energy increases
- Because of more protons/increased nuclear charge
- Electrons in the same energy level/shell
- No extra/similar shielding
- So stronger attraction between nucleus and outer/valence shell.
(stage 2) Deviation Be→B
- Lower than Be
- Outer electron in 2P
- Higher in energy than 2S
(Stage 3) Deviation N→O
- O Lower than N
- Electrons in 2(p) need to pair
- Pairing causes repulsion.
Explain why the first ionisation energy of the group 2 elements decreases down the group.
[2 marks] Jun2022/1
- The outer electron is in a higher energy level/ there is an increase in shielding as the atom has more shells
as the atom gets larger.
- There is a weaker attraction between the nucleus and the outer electron.
Explain why the third ionisation energy of magnesium is much higher than the second ionisation
energy of magnesium. [2 marks] Jun2022/1
- The electron is removed from 2p subshell compared to previous 3S/ Lower energy level/ therefore the
subshell is closer to the nucleus of the atom
- So the electron being removed is shielded less than 3s
Define the term electronegativity [1 mark] Jun2022/1
- The (relative) tendency of an atom to attract a pair of electrons/ the electrons/ electron density in a covalent
bond
The C-Br bond is polar. Explain why CBr4 is not a polar molecule. [2 marks] Jun2022/1
- the molecule is completely symmetrical / the molecule is tetrahedral / there is an even distribution of electron
density
- So the dipole moments cancel each other out.
1 Total questions: 48 (up to page 10)
, —Paper 1 Chemistry AS-Level AQA—
Suggest in terms of intermolecular forces for each compound, why CBr4 has a higher boiling
point than CHBR3 [3 marks] Jun2022/1
- CBr4 has van der waals’ forces between molecules
- CHBr3 has van der waals forces and dipole-dipole intermolecular forces.
- The van der Waals’ between CBr4 molecules are stronger than the dipole-dipole and van der Waals’ forces
between CHBr3 (because it has a larger mass/more electrons/larger electron cloud)
Explain how ions are detected and relative abundance is measured in a TOF mass spectrometer.
[2 marks] Jun2018/1
- Ion hits the detector/negative plate and gains an electron
- Relative abundance is proportional to the size of the current.
Silicon tetrafluoride (SiF4) is a tetrahedral molecule. Deduce the type of intermolecular forces in
SiF4 Explain how this type of intermolecular force arises and why no other type of intermolecular
force exists in a sample of SiF4 Intermolecular forces: Jun2018/1
- Van der waals forces
Explanation:
- Uneven distribution of electrons in one molecule induces a dipole in neighboring/ another molecule.
- Symmetrical molecular so no overall dipole moment (dipoles cancel out)
- No hydrogen bonds to F, so therefore no hydrogen bonding takes place.
There are two lone pairs of electrons on the oxygen atom in a molecule of oxygen difluoride (OF2).
Explain how the lone pairs of electrons on the oxygen atom influence the bond angle in oxygen
difluoride. [2 marks] Jun2018/1
- Lone pair repel more than bond pairs
- Bond angle will be lower than regular tetrahedral angle/bond angle of 103-106 degrees.
Identify the diagram in Figure 2 that shows the correct relative sizes of the ions in sodium
fluoride. Justify your answer. [3 marks] Jun2018/1
Diagram:
- B
Justification:
- Both Na+ and F- same electron arrangement (1s2 2s2 2p6 ) or isoelectronic
- Sodium ion has more protons so attracts outer /valence electrons closer
Give an equation, including state symbols, to represent the process that occurs when the third
ionisation energy of sodium is measured. [1 mark] Jun2020/1
- Na2+(g) → Na3+(g) + e−
Some of the liquid injected did not evaporate because it dripped into the gas syringe nozzle
outside the oven. Explain how this would affect the value of the Mr of Y calculated from the
experimental results. [2 marks] Jun2018/1
- Lower volume recorded
- Mr would be greater than real Mr
2 Total questions: 48 (up to page 10)
, —Paper 1 Chemistry AS-Level AQA—
Suggest how the procedure could be improved, using the same apparatus, to give a more
accurate value for x Justify your answer. [2 marks] Jun2018/1
- Heat till the mass remains constant
- You can be sure all/more of the water has been driven off.
There is a general trend for an increase in ionisation energy across Period 3. Give one example of an element
that deviates from this trend. Explain why this deviation occurs. [3 marks] Jun2022/1
Element:
- Al (Aluminium)
Explanation:
- Outer electron in 3p orbital/ subshell level
- 3p higher in energy/slightly more shielded than 3s and further away
Figure 1 shows the successive ionisation energies of a period 3 element, X.
Identify element X. And explain your choice [3 marks] Jun2020/1
Element:
- Phosphorus (P)
Explanation:
- There is a large jump in ionisation energy for the 6th ionisation energy.
- This is when the electron is being removed from the 2nd principle energy level from a lower energy level
shell/2p (closer to nucleus)
This question is about Group 2 elements and their compounds. Explain why the melting point of
magnesium is higher than the melting point of sodium. [2 marks] Jun2020/1
- Mg2+ has a higher charge than Na+ because of greater charge density.
- Stronger attraction to delocalised sea of electrons/stronger metallic bonding.
This question is about the group 2 metals Mg to Ba Strontium and calcium have the same metallic
structure. Explain why strontium has a lower melting point than calcium. [2 marks] Jun2025/1
- Sr has larger cations/positive ions
- Cation/positive ion has more electron shells/levels meaning greater shielding
- A positive ion has a lower charge density.
3 Total questions: 48 (up to page 10)
, —Paper 1 Chemistry AS-Level AQA—
The atomic radius decreases down group 2 from Mg to Ba gives a reason for this trend.
[1 mark] Jun2025/1
- More electron shells/energy levels
Molecules of CCl4 and CHCl3 have similar tetrahedral shapes.
The boiling point of CCl4 is 77 degrees
The boiling point of CHCl3 is 61 degrees
Explain why CCl4 has a higher boiling point than CHCl3. Your answer should:
- Explain why these molecules have a tetrahedral shape
- Explain why the molecules of each compound are polar or non-polar
- Compare the intermolecular forces in these compounds.
[6 marks] Jun2025/1
Stage 1- Shape:
- 4 bonding pairs and no lone pairs
- Each bonding pair repel as far as possible
Stage 2- polarity:
- C-Cl bonds are polar
- CCL4 is not polar as the overall dipole moment is 0 because the dipoles cancel out due to symmetry
- CH3Cl is polar because dipole moments do not cancel out/ asymmetric molecules.
Stage 3- boiling points
- CCl4 has van der waals’ forces
- CHCl3 had dipole-dipole forces and van der waals’ forces
- Van der waals’ forces in CCl4 is stronger than combined van der waals’ and dipole-dipole/ intermolecular
forces of CHCl3
- As Ccl4 has more electrons/ is a larger molecule.
SF6 and SF3 + have different shapes and different bond angles. Deduce the shape of SF6 and the
shape of SF3 + State the bond angle in SF6 and the bond angle in SF3 + Justify the bond angles
by referring to electron pairs. [6 marks] PMT B3
- SF6 is octahedral in shape
- SF6 bond angle is 90 degrees
- In SF6 all the bond repel equally
- SF3+ is trigonal pyramidal in shape
- SF3+ bond angle is 103-107 degrees
- Lone pair-bond repulsion is greater than pair-bond repulsion so bond angle is reduced.
Table 1 shows the boiling points of some halogens.
Explain the trend in the boiling points of these halogens. [2 marks] Jun2025/1
- Down the group
- Molecules are larger/ molecules contain more electrons so have larger surface area
- Stronger van der waals forces between molecules stronger/ stronger induced dipole.
Give the full electronic configuration of a fluoride ion (F-). Jun2025/1
- 1s2 2s2 2p6
4 Total questions: 48 (up to page 10)
Sodium fluoride contains sodium ions (Na+) and Fluoride ions (F-). Na+ and F- have the same
electron configuration. Explain why a fluoride ion is larger than a sodium ion.
[2 marks] Jun2019/1
- The fluoride ion has two fewer protons than the sodium ion / lower nuclear charge.
- Weaker attraction between nucleus and outer/valence electrons.
Explain in terms of structure and bonding, why the melting point of sodium fluoride is high.
[2 marks] Jun2019/1
- Electrostatic forces of attraction between oppositely charged ions Na+/F-
- A large amount of energy is needed to break/overcome these forces.
Describe how the molecules are ionised using electrospray ionisation. [3 marks] Jun2019/1
- The sample is dissolved in a volatile solvent.
- Injected through needle/nozzle capillary at high voltage/positively charged.
- Each molecule particle gains a proton/H+ ion.
The first ionisation energies of the elements in period 2 change as the atomic number increases.
Explain the pattern in the first ionisation energies of the elements from lithium to neon.
[ 6 marks] Jun2019/1
(Stage 1) general trend Li→Ne:
- 1st ionisation energy increases
- Because of more protons/increased nuclear charge
- Electrons in the same energy level/shell
- No extra/similar shielding
- So stronger attraction between nucleus and outer/valence shell.
(stage 2) Deviation Be→B
- Lower than Be
- Outer electron in 2P
- Higher in energy than 2S
(Stage 3) Deviation N→O
- O Lower than N
- Electrons in 2(p) need to pair
- Pairing causes repulsion.
Explain why the first ionisation energy of the group 2 elements decreases down the group.
[2 marks] Jun2022/1
- The outer electron is in a higher energy level/ there is an increase in shielding as the atom has more shells
as the atom gets larger.
- There is a weaker attraction between the nucleus and the outer electron.
Explain why the third ionisation energy of magnesium is much higher than the second ionisation
energy of magnesium. [2 marks] Jun2022/1
- The electron is removed from 2p subshell compared to previous 3S/ Lower energy level/ therefore the
subshell is closer to the nucleus of the atom
- So the electron being removed is shielded less than 3s
Define the term electronegativity [1 mark] Jun2022/1
- The (relative) tendency of an atom to attract a pair of electrons/ the electrons/ electron density in a covalent
bond
The C-Br bond is polar. Explain why CBr4 is not a polar molecule. [2 marks] Jun2022/1
- the molecule is completely symmetrical / the molecule is tetrahedral / there is an even distribution of electron
density
- So the dipole moments cancel each other out.
1 Total questions: 48 (up to page 10)
, —Paper 1 Chemistry AS-Level AQA—
Suggest in terms of intermolecular forces for each compound, why CBr4 has a higher boiling
point than CHBR3 [3 marks] Jun2022/1
- CBr4 has van der waals’ forces between molecules
- CHBr3 has van der waals forces and dipole-dipole intermolecular forces.
- The van der Waals’ between CBr4 molecules are stronger than the dipole-dipole and van der Waals’ forces
between CHBr3 (because it has a larger mass/more electrons/larger electron cloud)
Explain how ions are detected and relative abundance is measured in a TOF mass spectrometer.
[2 marks] Jun2018/1
- Ion hits the detector/negative plate and gains an electron
- Relative abundance is proportional to the size of the current.
Silicon tetrafluoride (SiF4) is a tetrahedral molecule. Deduce the type of intermolecular forces in
SiF4 Explain how this type of intermolecular force arises and why no other type of intermolecular
force exists in a sample of SiF4 Intermolecular forces: Jun2018/1
- Van der waals forces
Explanation:
- Uneven distribution of electrons in one molecule induces a dipole in neighboring/ another molecule.
- Symmetrical molecular so no overall dipole moment (dipoles cancel out)
- No hydrogen bonds to F, so therefore no hydrogen bonding takes place.
There are two lone pairs of electrons on the oxygen atom in a molecule of oxygen difluoride (OF2).
Explain how the lone pairs of electrons on the oxygen atom influence the bond angle in oxygen
difluoride. [2 marks] Jun2018/1
- Lone pair repel more than bond pairs
- Bond angle will be lower than regular tetrahedral angle/bond angle of 103-106 degrees.
Identify the diagram in Figure 2 that shows the correct relative sizes of the ions in sodium
fluoride. Justify your answer. [3 marks] Jun2018/1
Diagram:
- B
Justification:
- Both Na+ and F- same electron arrangement (1s2 2s2 2p6 ) or isoelectronic
- Sodium ion has more protons so attracts outer /valence electrons closer
Give an equation, including state symbols, to represent the process that occurs when the third
ionisation energy of sodium is measured. [1 mark] Jun2020/1
- Na2+(g) → Na3+(g) + e−
Some of the liquid injected did not evaporate because it dripped into the gas syringe nozzle
outside the oven. Explain how this would affect the value of the Mr of Y calculated from the
experimental results. [2 marks] Jun2018/1
- Lower volume recorded
- Mr would be greater than real Mr
2 Total questions: 48 (up to page 10)
, —Paper 1 Chemistry AS-Level AQA—
Suggest how the procedure could be improved, using the same apparatus, to give a more
accurate value for x Justify your answer. [2 marks] Jun2018/1
- Heat till the mass remains constant
- You can be sure all/more of the water has been driven off.
There is a general trend for an increase in ionisation energy across Period 3. Give one example of an element
that deviates from this trend. Explain why this deviation occurs. [3 marks] Jun2022/1
Element:
- Al (Aluminium)
Explanation:
- Outer electron in 3p orbital/ subshell level
- 3p higher in energy/slightly more shielded than 3s and further away
Figure 1 shows the successive ionisation energies of a period 3 element, X.
Identify element X. And explain your choice [3 marks] Jun2020/1
Element:
- Phosphorus (P)
Explanation:
- There is a large jump in ionisation energy for the 6th ionisation energy.
- This is when the electron is being removed from the 2nd principle energy level from a lower energy level
shell/2p (closer to nucleus)
This question is about Group 2 elements and their compounds. Explain why the melting point of
magnesium is higher than the melting point of sodium. [2 marks] Jun2020/1
- Mg2+ has a higher charge than Na+ because of greater charge density.
- Stronger attraction to delocalised sea of electrons/stronger metallic bonding.
This question is about the group 2 metals Mg to Ba Strontium and calcium have the same metallic
structure. Explain why strontium has a lower melting point than calcium. [2 marks] Jun2025/1
- Sr has larger cations/positive ions
- Cation/positive ion has more electron shells/levels meaning greater shielding
- A positive ion has a lower charge density.
3 Total questions: 48 (up to page 10)
, —Paper 1 Chemistry AS-Level AQA—
The atomic radius decreases down group 2 from Mg to Ba gives a reason for this trend.
[1 mark] Jun2025/1
- More electron shells/energy levels
Molecules of CCl4 and CHCl3 have similar tetrahedral shapes.
The boiling point of CCl4 is 77 degrees
The boiling point of CHCl3 is 61 degrees
Explain why CCl4 has a higher boiling point than CHCl3. Your answer should:
- Explain why these molecules have a tetrahedral shape
- Explain why the molecules of each compound are polar or non-polar
- Compare the intermolecular forces in these compounds.
[6 marks] Jun2025/1
Stage 1- Shape:
- 4 bonding pairs and no lone pairs
- Each bonding pair repel as far as possible
Stage 2- polarity:
- C-Cl bonds are polar
- CCL4 is not polar as the overall dipole moment is 0 because the dipoles cancel out due to symmetry
- CH3Cl is polar because dipole moments do not cancel out/ asymmetric molecules.
Stage 3- boiling points
- CCl4 has van der waals’ forces
- CHCl3 had dipole-dipole forces and van der waals’ forces
- Van der waals’ forces in CCl4 is stronger than combined van der waals’ and dipole-dipole/ intermolecular
forces of CHCl3
- As Ccl4 has more electrons/ is a larger molecule.
SF6 and SF3 + have different shapes and different bond angles. Deduce the shape of SF6 and the
shape of SF3 + State the bond angle in SF6 and the bond angle in SF3 + Justify the bond angles
by referring to electron pairs. [6 marks] PMT B3
- SF6 is octahedral in shape
- SF6 bond angle is 90 degrees
- In SF6 all the bond repel equally
- SF3+ is trigonal pyramidal in shape
- SF3+ bond angle is 103-107 degrees
- Lone pair-bond repulsion is greater than pair-bond repulsion so bond angle is reduced.
Table 1 shows the boiling points of some halogens.
Explain the trend in the boiling points of these halogens. [2 marks] Jun2025/1
- Down the group
- Molecules are larger/ molecules contain more electrons so have larger surface area
- Stronger van der waals forces between molecules stronger/ stronger induced dipole.
Give the full electronic configuration of a fluoride ion (F-). Jun2025/1
- 1s2 2s2 2p6
4 Total questions: 48 (up to page 10)
