Question

State the most stable oxidation state of Cr?

• A. 3
• B. 4
• C. 2
• D. 6

Answer 1

Answer: (A)

3

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. dxy dyz dxz are half filled.
Half filled $t_{2g}$ state is more stable than $d^5$ 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 in +1 oxidation state.

Hence option A is correct answer.