What this practice covers
These questions are drawn from past CIE 0620 Chemistry papers and filtered to isotopes. 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 isotopes, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Saying isotopes have different numbers of protons. Different protons means a different element.
- Saying isotopes have different numbers of electrons. Neutral atoms of any isotope have the same number as protons.
- Saying isotopes react differently. Their chemistry is identical because their electronic configurations are identical.
- Taking a simple mean of the isotope masses when the abundances are unequal. Chlorine would come out as 36 rather than 35.5.
- Forgetting to divide by 100 at the end, giving an answer in the thousands.
- Quoting a relative atomic mass with a unit. It is a ratio and has none.
- Rounding relative atomic mass to a whole number when the question asks for it from isotope data.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Isotopes revision notes.