A monitoring system records the numbers of protons and neutrons in two unstable nuclei before and after beta decay.
| record | protons before decay | neutrons before decay | protons after decay | neutrons after decay |
|---|---|---|---|---|
| P | 34 | 47 | 35 | 46 |
| Q | 26 | 24 | 25 | 25 |
Give the type of beta decay in each record.
Give the mass number and charge number of the particle emitted in record Q.
A third beta decay is represented by the incomplete equation
ZAX→3991Y+−10e {}^{A}_{Z}\mathrm{X} \rightarrow {}^{91}_{39}\mathrm{Y} + {}^{0}_{-1}\mathrm{e} ZAX→3991Y+−10eCalculate the number of neutrons in the nucleus of X before the decay.
Explain why the mass number stays the same in both records P and Q even though their atomic numbers change in opposite directions.