Edexcel A Level Chemistry June 2026 Paper 1, Paper 2 and
Paper 3 Markschemes Only [VERIFIED] Guaranteed Pass
Define first ionisation energy - answer - Energy required to remove one electron from
each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions
Define second ionisation energy - answer - Energy required to remove an electron (the
second electron) from each atom in a mole of gaseous 1+ ions producing one mole of 2+
gaseous ions
how does the number of protons affect ionisation energies - answer - the more protons,
the stronger the nuclear charge, resulting in stronger forces of attraction between the
nucleus and electrons, requiring more energy to break apart
how does the electron shielding affect ionisation energies - answer - the more electrons
between the electron getting removed and the nucleus, the lower the ionisation energy.
This is because the electrons repel the outer shell electron, balancing out some of the
positive charge/pull coming from the nucleus
how does the electron subshell the electron is being lost for affect ionisation energies -
answer - the closer the electron is to the nucleus, the stronger the forces will be therefore
requiring higher energies to overcome
1st ionisation energy down a group - answer - decreases
increase in shell number (larger atomic radii) and shielding outweighs the increase in
nuclear charge from greater number of protons
,1st ionisation energy across a period - answer - - Increasing trend due to greater proton
number and so atomic radii being drawn in
- dip at beginning of p orbital due to being easier to lose than second electron in s orbital
- dip at third last due to being the first electron in a pair in the p-orbitals, the two
electrons repel each other, lowering energy required
trend in successive ionisation energies - answer - every time goes up, big leap when
going down a quantum shell
equation representing first ionisation energy of x atoms - answer - X₍g₎ --> X⁺₍g₎ + e⁻
how to calculate relative atomic mass from relative abundance of isotopes - answer - (%₁
x mass₁) + (%₂ x mass₂) + .....
how to calculate peak heights for diatomic molecules - answer - relative abundance of the
isotopes, the probability of each combination makes the ratio
how to work out relative molecular mass of a molecule from mass spectra - answer -
furthest right peak will be all atoms together
What is an M+1 peak - answer - occurs due to the natural abundance of the carbon-13
isotope, which increases mass number of normal molecule by 1
,how to predict mass spectra of a molecule - answer - analyse different individual possible
fragments and their stability, the more stable, the more likely they are to occur, therefore
likely having a higher abundance. There will be a line at every possible mass number of
each of the fragments
how does atomic emission spectra provide evidence for the existence of quantum shells -
answer - Spectral lines give evidence of electrons moving from one energy level to
another within the atom
how do successive ionisations provide evidence for the existence of quantum shells -
answer - Successive ionisations of an atom suggest that there are energy shells with large
energy differences between them.
why do atoms emit light when heated - answer - it is the energy required to allow
electrons to jump back and forth across shells
What is periodicity - answer - the repeating pattern of chemical and physical properties of
the elements with increasing atomic number
what is an orbital - answer - most probable region where you can find an electron
can hold up to two electrons with opposite spins
number of electrons that fit in the 1st, 2nd, 3rd and 4th quantum shells - answer -
2,8,18,32
, shape of an s-orbital - answer -
shape of a p-orbital - answer - can have 3 different orientations - x,y,z
how many electrons and orbitals does a s subshell hold - answer - 2 electrons in
1 spherical s orbital
how many electrons and orbitals does a p subshell hold - answer - 6 electrons in
3 dumbbell shaped p orbitals
how many electrons and orbitals does a d subshell hold - answer - 10 electrons in
5 orbitals
how do electrons fill orbitals - answer - they fill subshells by entering each orbital singly,
before then pairing up to fill the subshell. The two electrons in each orbital must have
opposite spins
box notation of a full s subshell - answer - one box with two arrows, one up, one down
box notation of a full p subshell - answer - three boxes with each having two arrows, one
up, one down
Paper 3 Markschemes Only [VERIFIED] Guaranteed Pass
Define first ionisation energy - answer - Energy required to remove one electron from
each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions
Define second ionisation energy - answer - Energy required to remove an electron (the
second electron) from each atom in a mole of gaseous 1+ ions producing one mole of 2+
gaseous ions
how does the number of protons affect ionisation energies - answer - the more protons,
the stronger the nuclear charge, resulting in stronger forces of attraction between the
nucleus and electrons, requiring more energy to break apart
how does the electron shielding affect ionisation energies - answer - the more electrons
between the electron getting removed and the nucleus, the lower the ionisation energy.
This is because the electrons repel the outer shell electron, balancing out some of the
positive charge/pull coming from the nucleus
how does the electron subshell the electron is being lost for affect ionisation energies -
answer - the closer the electron is to the nucleus, the stronger the forces will be therefore
requiring higher energies to overcome
1st ionisation energy down a group - answer - decreases
increase in shell number (larger atomic radii) and shielding outweighs the increase in
nuclear charge from greater number of protons
,1st ionisation energy across a period - answer - - Increasing trend due to greater proton
number and so atomic radii being drawn in
- dip at beginning of p orbital due to being easier to lose than second electron in s orbital
- dip at third last due to being the first electron in a pair in the p-orbitals, the two
electrons repel each other, lowering energy required
trend in successive ionisation energies - answer - every time goes up, big leap when
going down a quantum shell
equation representing first ionisation energy of x atoms - answer - X₍g₎ --> X⁺₍g₎ + e⁻
how to calculate relative atomic mass from relative abundance of isotopes - answer - (%₁
x mass₁) + (%₂ x mass₂) + .....
how to calculate peak heights for diatomic molecules - answer - relative abundance of the
isotopes, the probability of each combination makes the ratio
how to work out relative molecular mass of a molecule from mass spectra - answer -
furthest right peak will be all atoms together
What is an M+1 peak - answer - occurs due to the natural abundance of the carbon-13
isotope, which increases mass number of normal molecule by 1
,how to predict mass spectra of a molecule - answer - analyse different individual possible
fragments and their stability, the more stable, the more likely they are to occur, therefore
likely having a higher abundance. There will be a line at every possible mass number of
each of the fragments
how does atomic emission spectra provide evidence for the existence of quantum shells -
answer - Spectral lines give evidence of electrons moving from one energy level to
another within the atom
how do successive ionisations provide evidence for the existence of quantum shells -
answer - Successive ionisations of an atom suggest that there are energy shells with large
energy differences between them.
why do atoms emit light when heated - answer - it is the energy required to allow
electrons to jump back and forth across shells
What is periodicity - answer - the repeating pattern of chemical and physical properties of
the elements with increasing atomic number
what is an orbital - answer - most probable region where you can find an electron
can hold up to two electrons with opposite spins
number of electrons that fit in the 1st, 2nd, 3rd and 4th quantum shells - answer -
2,8,18,32
, shape of an s-orbital - answer -
shape of a p-orbital - answer - can have 3 different orientations - x,y,z
how many electrons and orbitals does a s subshell hold - answer - 2 electrons in
1 spherical s orbital
how many electrons and orbitals does a p subshell hold - answer - 6 electrons in
3 dumbbell shaped p orbitals
how many electrons and orbitals does a d subshell hold - answer - 10 electrons in
5 orbitals
how do electrons fill orbitals - answer - they fill subshells by entering each orbital singly,
before then pairing up to fill the subshell. The two electrons in each orbital must have
opposite spins
box notation of a full s subshell - answer - one box with two arrows, one up, one down
box notation of a full p subshell - answer - three boxes with each having two arrows, one
up, one down
