Question

If Hund's rule violated, then how many unpaired electron(s) is/are present in [Cr(NH${}_3$)${}_6$]${}^{3+}$ complex ion?

• A. 1
• B. 2
• C. 3
• D. None

Answer 1

The correct option is A 1

$\left[Cr\right(N{H}_3{)}_6{]}^{3+}$
Cr is in +3 oxidation state.
$C{r}^{3+}-\left[Ar\right]3d^3$
$N{H}_3$ is a strong field ligand so it will pair the electron. Then only one unpaired electron will remain in 3d orbital.