Question

Assertion : The degree of complex formation in actinides decreases in the order $M^{4+} > MO_2^{2+} > M^{3+} > MO_2^+$.
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

$M^{4+} > MO_{2}^{2+} > M^{3+} > MO_{2}^{+}$

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