What this practice covers
These questions are drawn from past CIE 9701 Chemistry papers and filtered to atomic structure. You answer, you find out immediately whether you were right, and you get the reasoning for the correct option and for each distractor. Wrong answers go to a mistakes locker so you can come back to exactly those.
Practice is free. You need an account only so your progress and your mistakes are still there next time.
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What examiners see students get wrong here
These are the errors that cost marks on atomic structure, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Changing the number of neutrons when an ion forms. Only electrons are gained or lost.
- Writing Fe²⁺ as 3d⁴ 4s². The 4s electrons go first, so it is 3d⁶.
- Leaving "gaseous" or "one mole" out of the ionisation energy definition.
- Saying the atomic radius increases across a period. It decreases, because the nuclear charge grows while shielding stays about the same.
- Explaining the Mg to Al dip with shielding. The reason is the sub-shell: the electron comes from 3p rather than 3s.
- Explaining the P to S dip with nuclear charge. The reason is paired electron repulsion within one p orbital.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Atomic structure revision notes.