Physics (AS & A Level) · Oct / Nov 2017 · Paper 13 · Question 39

Each option shows the number of neutrons, protons and electrons in two atoms, some of which are ionised. Which pair of atoms in the table are isotopes of the same element?

1. Aneutron 20 20, proton 17 19, electron 20 20
2. Bneutron 28 28, proton 23 24, electron 23 24
3. Cneutron 34 36, proton 29 29, electron 29 28
4. Dneutron 40 42, proton 32 31, electron 32 32

As printed in the paper