$\quad\quad\quad\quad\quad\quad{Mg}$ $\quad\quad{Al}$ $\quad\quad\quad{P}$ $\quad\quad\quad{S}$

Valence $\left[{N}_{{e}}\right]: 3 {~s}^{2}$ $\quad3 {~s}^{2} 3 {p}^{1}$ $\quad3 {~s}^{2} 3 {p}^{3} \quad3 {~s}^{2} 3 {p}^{4}$

$\quad\quad\quad\quad\quad\quad\uparrow$ $\quad\quad\quad\quad\quad\quad\uparrow$

$\quad\quad\quad\quad\quad$Full Filled Stable $\quad$Half Filled Stable