Which of the following is diamagnetic in nature ?

Options

A. `Co^(3+)` , octahedral complex with weak field ligands
B. `Co^(3+)`, octahedral complex with strong field ligands
C. `Co^(2+)` in tetrahedral complex
D. `Co^(2+)` in a square planar complex.

Answer

B

Explanation

`_(27)Co = 3d^(7)4s^(2), Co^(3+)` = `3d^(6)4s^(0)`

In a strong field ligand , electrons pair up.
`:.`It is diamagnetic in nature.