Question

For which of the following types of ions is the number of unpaired electrons in octahedral complexes fixed at the same number as in the free ion no matter, how weak or strong the crystal field is?

• A. $d^3$
• B. $d^4$
• C. $d^5$
• D. $d^6$

Answer 1

The correct option is A $d^3$

For $d^3$ configuration, the number of unpaired electrons is 3. It is irrespective of the strength of the ligand field.
This is because, three electrons enter $t_{2g}$ level and are unpaired. When fourth electron is present its position (in $t_{2g}$ or $-g$ level) will be determined by the strength of the ligand field.