Sodium-24 (1124Na^{24}_{11}\text{Na}1124Na) is an isotope of sodium.
a.
[2]
Which of the isotopes given in Table 1 is not an isotope of sodium? Give a reason for your answer.
Table 1
| Isotope | Mass number | Atomic number |
|---|---|---|
| P | 23 | 11 |
| Q | 23 | 12 |
| R | 22 | 11 |
b.[1]
How many hours does it take for the number of sodium-24 nuclei to decrease from 12000 to 6000?
c.[1]
What is the half-life of sodium-24?