Question

Which statement regarding [Cr(NH3)6]^3+ is incorrect?

(a) It has octahedral geometry

(b) It has d^2sp^3 hybridisation

(c) It is diamagnetic

(d) It is a low spin complex

I had been asked this question by my school teacher while I was bunking the class.

This intriguing question originated from Bonding in Coordination Compounds topic in portion Coordination Compounds of Chemistry – Class 12

Answer 1

The correct answer is (c) It is diamagnetic

Easiest explanation: Cr^3+ has six empty orbitals- two 3d, one 4s and three 4p orbitals, which are occupied by six electron pairs from six NH3 molecules to form six d^2sp^3 hybridised orbitals. This leaves, three unpaired 3d electrons, making it paramagnetic. Also, since the inner d orbitals are involved, it is a low spin complex.