The table shows the numbers of particles in a nucleus before and after one decay.
| Protons | Neutrons | |
|---|---|---|
| Before | 15 | 15 |
| After | 14 | 16 |
Which particle is emitted, and what happens to the mass number?
An electron is emitted; the mass number decreases by one.
A positron is emitted; the mass number decreases by one.
A positron is emitted; the mass number is unchanged.
An electron is emitted; the mass number is unchanged.
120 exam-style questions on Edexcel GCSE Physics 6.3 Nuclear equations and decay, covering 6.3.1 Beta-minus and beta-plus decay, 6.3.2 Effects of decay on the nucleus, and 6.3.3 Balancing nuclear equations. Each one has a worked solution and a mark scheme showing where the marks go.