Question

Assertion (A) Actinoids form relatively less stable complexes as compared to lanthanoids.
Reason (R) Actinoids can utilise their $5f$-orbitals alongwith $6d$-orbitals in bonding but lanthanoids do not use their $4f$-orbital for bonding.

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are correct; $R$ is not the correct explanation of $A$.
• C. $A$ is correct; $R$ is incorrect.
• D. $R$ is correct; $A$ is incorrect.

Answer 1

Answer: (D)

Assertion is incorrect but reason is correct. Actinoids form relatively more stable complexes as compared to lanthanoids because of actinoids can utilise their $5f$-orbitals along with $6d$-orbitals in bonding but lanthanoids do not use their $4f$-orbitals for bonding.