Given below are two statements: one is labelled as Assertion A and...

Mg have $2$ electrons in valance shell and after donation of $2$electrons it converts into ${Mg}^{2 +}$ ion and attains inert gas configuration, now to ionize one more electron from inert gas configuration is very difficult, hence it is easy to ionize $Mg$ to${Mg}^{2 +}$. ${IE}_{2}$ is always greater than ${IE}_{1}$ because on removal of ${e}^{-}$, size decreases and effective nuclear charge increases.So Assertion is correct.

${Mg}^{2 +}$ is a smaller ion than ${Mg}^{+}$ and has a greater charge density. This means that ${Mg}^{2 +}$ has a stronger attraction to its electrons than ${Mg}^{+}$ and requires more energy to remove an electron from it. So reason is also correct.