Question

The maximum sum of $(n+l+m)$ values for unpaired electrons in the excited state of sulphur where it shows maximum covalency is:

• A. 28
• B. 25
• C. 20
• D. 27

Answer 1

The correct option is A 28

Electronic configuration of sulphur (atomic no. = 16)
at the ground state: $=\left[Ne\right]3s^{2}3p^4$
excited state: $=\left[Ne\right]3s^{1}3p^{3}3d^2$
S has 6 unpaired electrons in its excited state where it has maximum covalency.
For $3s^1$,
$n=3,l=0,m=0$
$\therefore n+l+m=3$
For $3p^3$,
$n=3,l=1,m=+1,0,-1$
$\therefore n+l+m=(3+1+1)+(3+1+0)+(3+1-1)$
$=12$
For $3d^2$,
$n=3,l=2,m=+2,+1$
$\therefore n+l+m=(3+2+2)+(3+2+1)$
$=13$

Total value becomes
$=3+12+13=28$