Bismuth-210 $\left( {_{\;83}^{210}{\text{Bi}}} \right)$ is a radioactive isotope that decays as follows.

$$_{\;83}^{210}{\text{Bi}}\xrightarrow{{{\beta ^ - }}}{\text{X}}\xrightarrow{\alpha }{\text{Y}}$$

What are the mass number and proton number of Y?

B