sblock Elements 1 Question 18
14. The total number of isotopes of hydrogen and number of radioactive isotopes among them, respectively, are
(2019 Main, 10 Jan I)
(a) 2 and 1
(b) 3 and 2
(c) 2 and 0
(d) 3 and 1
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Solution:
- Hydrogen has three isotopes:
| ${ }_{1}^{1} \mathbf{H}$ | ${ }_{1}^{2} \mathbf{H}$ | ${ }_{1}^{3} \mathbf{H}$ | |
|---|---|---|---|
| Protium (P) | Deuterium (D) | Tritium (T) | |
| $p$ | 1 | 1 | 1 |
| $n$ | 0 | 1 | 2 |
| $\frac{n}{p}$ | 0 | 1 | 2 |
Only tritium (T) is radioactive, because of its very high $\frac{n}{p}$ value, $\left(\frac{n}{p}=2\right)$.
