Question

Which one of the following statement is correct for $d^4$ ions [P$=$ pairing energy]?

• A. When ${\Delta }_0>P$, low-spin complex form
• B. When ${\Delta }_0<P$, low-spin complex form
• C. When ${\Delta }_0>P$, high-spin complex form
• D. When ${\Delta }_0<P$, both high-spin and low-spin complexes form

Answer 1

The correct option is A When ${\Delta }_0>P$, low-spin complex form

The following statement is correct for $d^4$ ions [P$=$ pairing energy].
When ${\Delta }_0>P$, low-spin complex form.
The fourth electron occupies $t_{2g}$ level and tends to pair.
Low-spin complex is also called strong field or spin paired octahedral complex ion.
Note:
When ${\Delta }_0<P$, high-spin complex form.
The fourth electron occupies $e_g$ level and remains unpaired.
High-spin complex is also called weak field or spin free octahedral complex ion.