A monitoring system records the mass number and atomic number during a two-stage nuclear decay process.
| measurement | mass number | atomic number |
|---|---|---|
| before the first emission | 150 | 62 |
| after the first emission | 150 | 63 |
| after the second emission | 146 | 61 |
Three records give different accounts of the process.
| record | first emission | second emission |
|---|---|---|
| P | alpha | beta-minus |
| Q | beta-minus | alpha |
| R | beta-plus | alpha |
Evaluate which record is consistent with all the measurements.
The measurement made after the first emission is lost.
Explain why the remaining measurements cannot show whether record P or record Q gives the correct order.