Question

Chromium forms most stable compound in the following oxidation state is:

• A. $Cr\left(I\right)$
• B. $Cr$
• C. $Cr\left(III\right)$
• D. $Cr\left(IV\right)$

Answer 1

The correct option is C $Cr\left(III\right)$

Chromium has ground state configuration of $\left[Ar\right]3d^{5}4s^1$. After it has attained a configuration of +3 its electronic configuration becomes $\left[Ar\right]3d^3$, this makes it half filled stable at the $t_{2g}$ level which means three sub-d orbitals i.e. $d_{xy}$, $d_{yz}$ and $d_{xz}$ are half filled. Half filled $t_{2g}$ state is more stable than d5 configuration so ,Chromium is more stable in its $d^3$ state than its $d^5$ state. Hence chromium is more stable in +3 oxidation state than any other oxidation state.