$\mathrm{Na} \rightarrow[\mathrm{Ne}] 3 \mathrm{~s}^1 \mathrm{IE}_1$ is very low but $\mathrm{IE}_2$ is very high due to stable noble gas configuration of $\mathrm{Na}^{+}$. $\mathrm{Mg} \rightarrow[\mathrm{Ne}] 3 \mathrm{~s}^2 \mathrm{IE}_1$ \& $\mathrm{IE}_2 \rightarrow$ Low $\mathrm{IE}_3$ is very high.