AQA A-LEVEL CHEMISTRY STUDY GUIDE
REVIEW 2026 PRECISE ANSWERS
GRADED A+
◉ What is the charge of a neutron? Answer: 0
◉ What is the charge of an electron? Answer: -1
◉ What is the mass of a proton? Answer: 1
◉ What is the mass of a neutron? Answer: 1
◉ What is the mass of an electron? Answer: 1/1800
◉ What is an isotope? Answer: Isotopes of an element are atoms
with the same number of protons but different numbers of neutrons.
◉ Why do isotopes of an element all have the same chemical
properties? Answer: This is because chemical properties are decided
by the number and arrangements of electrons and all isotopes of an
element have the same number of electrons.
,◉ Why do isotopes of an element have different physical properties?
Answer: This is because physical properties are decided by the mass
number and isotopes of an element have different mass numbers.
◉ What is the first stage in time of flight mass spectrometry and
what are the 2 ways it can occur? Answer: 1. Electron spray ionisation
2.Electron impact ionisation
◉ What is electron spray ionisation? Answer: The sample is
dissolved and pushed through a small nozzle at high pressure. A high
voltage is applied to it causing each particle to gain a + ion so that the
gas is made up of positive ions.
◉ What is electron impact ionisation? Answer: The sample is
vaporised and an electron gun is used to fire high energy electrons
which knocks of 1 electron of each particle so they become positive
ions.
◉ What is the second stage in time of flight mass spectrometry?
Answer: Acceleration
◉ What happens in the acceleration stage of time of flight mass
spectrometry? Answer: The positively charged ions are accelerated
by an electric field so that they all have the same kinetic energy
which means that the lighter ions will move faster than the heavier
ions.
,◉ What is the third stage in time of flight mass spectrometry?
Answer: Ion drift
◉ What happens in the ion drift stage of time of flight mass
spectrometry? Answer: The ions enter a region with no electric field,
so they just drift through it. Lighter ions will drift through faster than
heavier ions.
◉ What is the final stage of time of flight mass spectrometry?
Answer: Detection
◉ What happens in the detection stage of time of flight mass
spectrometry? Answer: Because ions have a lower mass/charge ratio
travel at a higher speed in the drift region, they reach the detector in
less time than ions with a higher mass/charge ratio. The detector
detects charged particles and a mass spectrum is produced.
◉ What is the electronic configuration of calcium? Answer:
1s2,2s2,2p6,3s2,3p6,4s2
◉ What is the electronic configuration of chromium? Answer:
1s2,2s2,2p6,3s2,3p6,3d5,4s1
, ◉ What is the first ionisation energy? Answer: The first ionisation
energy needed to remove one electron from each atom in 1 mole of
gaseous atoms to form 1 mole of +1 gaseous ion..
◉ How does nuclear charge affect ionisation energy? Answer: More
protons means more positively charged means the stronger the
attraction for electrons.
◉ How does distance from the nucleus affect ionisation energy?
Answer: The closer the electron is to the nucleus, the stronger the
attraction.
◉ How does shielding affect ionisation energy? Answer: As the
number of electrons between outer electrons and the nucleus
increases, the outer electron feels less attraction towards the nuclear
charge.
◉ What is the trend in ionisation energy down a group? Answer: The
first ionisation energy down a group has a general decrease because
down a group each element has an extra electron shell compared to
the one above so the extra inner shells will shield the outer electrons
from the nucleus attraction.
◉ What is the trend in ionisation energy across a period? Answer:
The first ionisation energy across a period has a general increase
because it gets harder to remove outer shell electrons.
REVIEW 2026 PRECISE ANSWERS
GRADED A+
◉ What is the charge of a neutron? Answer: 0
◉ What is the charge of an electron? Answer: -1
◉ What is the mass of a proton? Answer: 1
◉ What is the mass of a neutron? Answer: 1
◉ What is the mass of an electron? Answer: 1/1800
◉ What is an isotope? Answer: Isotopes of an element are atoms
with the same number of protons but different numbers of neutrons.
◉ Why do isotopes of an element all have the same chemical
properties? Answer: This is because chemical properties are decided
by the number and arrangements of electrons and all isotopes of an
element have the same number of electrons.
,◉ Why do isotopes of an element have different physical properties?
Answer: This is because physical properties are decided by the mass
number and isotopes of an element have different mass numbers.
◉ What is the first stage in time of flight mass spectrometry and
what are the 2 ways it can occur? Answer: 1. Electron spray ionisation
2.Electron impact ionisation
◉ What is electron spray ionisation? Answer: The sample is
dissolved and pushed through a small nozzle at high pressure. A high
voltage is applied to it causing each particle to gain a + ion so that the
gas is made up of positive ions.
◉ What is electron impact ionisation? Answer: The sample is
vaporised and an electron gun is used to fire high energy electrons
which knocks of 1 electron of each particle so they become positive
ions.
◉ What is the second stage in time of flight mass spectrometry?
Answer: Acceleration
◉ What happens in the acceleration stage of time of flight mass
spectrometry? Answer: The positively charged ions are accelerated
by an electric field so that they all have the same kinetic energy
which means that the lighter ions will move faster than the heavier
ions.
,◉ What is the third stage in time of flight mass spectrometry?
Answer: Ion drift
◉ What happens in the ion drift stage of time of flight mass
spectrometry? Answer: The ions enter a region with no electric field,
so they just drift through it. Lighter ions will drift through faster than
heavier ions.
◉ What is the final stage of time of flight mass spectrometry?
Answer: Detection
◉ What happens in the detection stage of time of flight mass
spectrometry? Answer: Because ions have a lower mass/charge ratio
travel at a higher speed in the drift region, they reach the detector in
less time than ions with a higher mass/charge ratio. The detector
detects charged particles and a mass spectrum is produced.
◉ What is the electronic configuration of calcium? Answer:
1s2,2s2,2p6,3s2,3p6,4s2
◉ What is the electronic configuration of chromium? Answer:
1s2,2s2,2p6,3s2,3p6,3d5,4s1
, ◉ What is the first ionisation energy? Answer: The first ionisation
energy needed to remove one electron from each atom in 1 mole of
gaseous atoms to form 1 mole of +1 gaseous ion..
◉ How does nuclear charge affect ionisation energy? Answer: More
protons means more positively charged means the stronger the
attraction for electrons.
◉ How does distance from the nucleus affect ionisation energy?
Answer: The closer the electron is to the nucleus, the stronger the
attraction.
◉ How does shielding affect ionisation energy? Answer: As the
number of electrons between outer electrons and the nucleus
increases, the outer electron feels less attraction towards the nuclear
charge.
◉ What is the trend in ionisation energy down a group? Answer: The
first ionisation energy down a group has a general decrease because
down a group each element has an extra electron shell compared to
the one above so the extra inner shells will shield the outer electrons
from the nucleus attraction.
◉ What is the trend in ionisation energy across a period? Answer:
The first ionisation energy across a period has a general increase
because it gets harder to remove outer shell electrons.
