Question

Does $\mathrm{Na}\mathrm{or}\mathrm{Mg}$have higher ionization energy?

Answer 1

• Ionization energy is the energy liberated when electron is removed from the isolated gaseous atom
• 
• Magnesium $\left(\mathrm{Mg}\right)$ has higher ionization energy than sodium $\left(\mathrm{Na}\right)$.

$$\begin{gathered} \mathrm{Configuration}\mathrm{of}\mathrm{Na}=1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1 \\ \mathrm{Configuration}\mathrm{of}\mathrm{Mg}=1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2 \end{gathered}$$

• The more stable electronic configuration has a greater ionization energy.
• Sodium outer electronic configuration is $3{\mathrm{s}}^1$while for magnesium it is $3{\mathrm{s}}^2$. As magnesium has a completely filled $\mathrm{s}$ orbital , it's ionization energy is greater than sodium. (half filled and full filled orbitals are more stable)