A detector records two successive emissions from an unstable nucleus that initially contains 85 protons and 126 neutrons. The labels identifying the emissions are missing from the record.
| Emission stage | Mass number of emission | Charge number of emission |
|---|---|---|
| first | 4 | +2 |
| second | 0 | 0 |
After the second emission, the nucleus is in a lower energy arrangement.
A student concludes that the final nucleus contains 122 neutrons because the first emission has a mass number of 4.
Explain whether the student's conclusion is correct.
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.