The maximum no. or electrons in phosphorous atom for which n + I + m = 3 will be :

The electronic configuration is,

$P_{1s}\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^3$

Here, the total number of electron with n+m+l=3 can be given as

2 (for p with $\pm \frac{1}{2}$ spin), $+2$ (for 39 with $\pm \frac{1}{2}$spin)
$+1$ (for $3\mathrm{p}$ as it has only single electron)
5 electrons.