Question

Among the following complexes, the one which shows zero crystal field stabilisation energy (CFSE) is ______.

Options

• [Mn(H₂O)₆]³⁺

• [Fe(H₂O)₆]³⁺

• [Co(H₂O)₆]²⁺

• [Co(H₂O)₆]³⁺

Answer 1

Among the following complexes, the one which shows zero crystal field stabilisation energy (CFSE) is `bbunderline([Fe(H_2O)_6]^(3+))`.

Explanation:

• [Fe(H₂O)₆]³⁺ in the complex Fe³⁺ has a d⁵ configuration. In an octahedral crystal field, the five electrons fill the t₂g and eg orbitals equally (one electron per orbital), leading to zero CFSE. This is because the electrons are symmetrically distributed and there is no net stabilization from the field.
• The other complexes have non-zero CFSE because their electron configurations result in unequal distribution of electrons in the t₂g and eg orbitals, causing energy differences and net stabilization.