Question

Identify the Lanthanoid ions having half filled and completely filled 4f orbitals respectively.

• A. \(\text{Eu}^{2+}\) and \(\text{Tm}^{2+}\)
• B. \(\text{Sm}^{2+}\) and \(\text{Tm}^{3+}\)
• C. \(\text{Tb}^{4+}\) and \(\text{Yb}^{2+}\)
• D. \(\text{Dy}^{3+}\) and \(\text{Yb}^{3+}\)

Hint:

Half-filled 4f means 4f7 and completely filled means 4f14. Find the pair of ions that reach these configurations after losing electrons.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
A half-filled 4f subshell holds \(4f^{7}\) and a completely filled one holds \(4f^{14}\). Write the configuration of each ion and count the 4f electrons.

Step 2: Calculation
Tb is \([\text{Xe}]4f^{9}6s^{2}\). Losing two 6s and two 4f electrons gives \(\text{Tb}^{4+}\) with \(4f^{7}\), which is half-filled.
Yb is \([\text{Xe}]4f^{14}6s^{2}\). Losing two 6s electrons gives \(\text{Yb}^{2+}\) with \(4f^{14}\), which is completely filled.

Step 3: Compare the options
\(\text{Eu}^{2+}\) is \(4f^{7}\) but \(\text{Tm}^{2+}\) is \(4f^{13}\). \(\text{Sm}^{2+}\) is \(4f^{6}\) and \(\text{Dy}^{3+}\) is \(4f^{9}\). Only option (C) fits both conditions.

Final Answer:
The half-filled and completely filled ions are Tb4+ and Yb2+ respectively. \[ \boxed{\text{(C) }\text{Tb}^{4+}\text{ and }\text{Yb}^{2+}} \]