Question

Technetium ${(}_{43}^{98}Tc)$ has a half - life of $4.2\times {10}^{6}yr$. Strontium has a half - life of 28.79 yr. which of the following is correct?

• A. Decay constant of Sr is greater than decay constant of Tc
• B. Activity of 100 g of Sr is less than activity of 100 g of Tc
• C. The long half - life of Tc shows that it decays by $\alpha$ - decay
• D. A Tc atom has a higher probability of decaying in 1 yr than a Sr atom

Answer 1

The correct option is A Decay constant of Sr is greater than decay constant of Tc

Decay constant, $\lambda =\frac{lo{g}_2}{T_{1/2}}$
As,$T_{\frac{1}{2}}\left(Te\right)>T_{\frac{1}{2}}\left(Sr\right)$
$\Rightarrow \lambda \left(Te\right)<\lambda \left(Sr\right)$
(All other options are incorrect)