A chemist is choosing samples to test a machine that separates isotopes. Each sample contains only one type of neutral atom. The chemist needs two samples whose atoms are isotopes of the same element and take part in chemical reactions in the same way.
The table shows information about the atoms in each sample.
| Sample | Atomic number | Mass number |
|---|---|---|
| P | 20 | 40 |
| Q | 18 | 40 |
| R | 20 | 44 |
Evaluate which two samples the chemist should choose.
101 exam-style questions on OCR GCSE Chemistry 1.2 Atomic structure, covering 1.2.1 Development of the atomic model, 1.2.2 The nuclear model and the size of atoms, and 1.2.3 Subatomic particles in atoms and ions. Each one has a worked solution and a mark scheme showing where the marks go.