Question

Assertion : The degree of complex formation in actinides decreases in the order $M^{4+}>M{O}_2^{2+}>M^{3+}>M{O}_2^{+}$.
Reason : Actinides form complexes with $\pi$-bonding ligands such as alkyl phosphines and thioethers.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

The higher the charge on the metal ion, smaller is the ionic size and more is the complex forming ability. Thus, the degree of complex formation decreases in the order

$M^{4+}>M{O}_2^{2+}>M^{3+}>M{O}_2^{+}$

The higher tendency of complex formation of $M{O}_2^{2+}$ as compared to $M^{3+}$ is due to high concentration of charge on metal atom M in $M{O}_2^{2+}$.