Question

The three isotopes

$$\begin{gathered} {}^{212}\mathrm{Po},{}^{137}\mathrm{Cs},\text{and}{}^{90}\mathrm{Sr}\text{decay as}{}^{212}\mathrm{Po}\to {}^{208}\mathrm{Pb}+\alpha ,{}^{137}\mathrm{Cs}\to {}^{137}\mathrm{Ba}+{\mathrm{e}}^{-}+\gamma , \\ \text{and}{}^{90}\mathrm{Sr}\to {}^{90}\mathrm{Y}+{\mathrm{e}}^{-} \end{gathered}$$Which of these isotopes would be most useful as a biological tracer? Why?

Short answer

Thus,$C{s}^{137}$ would be quite valuable.

Step-by-step solution

Given information

Three isotopes are given:

$$\begin{gathered} {}^{212}\mathrm{Po},{}^{137}\mathrm{Cs},\text{and}{}^{90}\mathrm{Sr}\text{decay as}{}^{212}\mathrm{Po}\to {}^{208}\mathrm{Pb}+\alpha ,{}^{137}\mathrm{Cs}\to {}^{137}\mathrm{Ba}+{\mathrm{e}}^{-}+\gamma , \\ \text{and}{}^{90}\mathrm{Sr}\to {}^{90}\mathrm{Y}+{\mathrm{e}}^{-} \end{gathered}$$

Explanation

Because a gamma ray is emitted after beta decay, $C{s}^{137}$would be quite valuable. Because alphas and betas do not penetrate material well, they would not be discovered if they were to escape the body.

Explanation

However, the gamma ray does enter material well and might be identified if it were to escape the body.