${\mathrm{Mg}}^{2+}\text{ and }\mathrm{Al}{l}^{3+}\text{ have same }$

The atomic number of magnesium (Mg) is 12.

So, it has total 12 protons, 12 neutrons and 12 electrons of in neutral atom.

The atomic number of aluminum (Al) is 13.

So, it has total 13 protons, 14 neutrons and 13 electrons of in neutral atom.

$\text{ Electronic configuration of }\mathrm{Mg}\text{ is }1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2\text{. }$$\text{ Electronic configuration of }{\mathrm{Mg}}^{+2}\text{ is }1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6\text{ or }\left[\mathrm{Ne}\right]$$\text{ Electronic configuration of }\mathrm{Al}\text{ is }1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^1$$\text{ Electronic configuration of }{\mathrm{Al}}^{+3}\text{ is }1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^6\text{ or [Ne] }$$$\begin{gathered} \text{ Therefore, both }{\mathrm{Mg}}^{+2}\text{ and }{\mathrm{Al}}^{+3}\text{ ions have the same}\text{electronic } \\ \text{configuration. } \end{gathered}$$