Question

Electronic configuration of Gd (64) is written as

• A. [Xe] \(4f^7 5d^1 6s^2\)
• B. [Xe] \(4f^8 6s^2\)
• C. [Xe] \(4f^9 6s^1\)
• D. [Xe] \(4f^{10}\)

Hint:

Exceptions: Gd (\(4f^7 5d^1 6s^2\)) and Lu (\(4f^{14} 5d^1 6s^2\)) have 5d\(^1\) electron.

Answer 1

The Correct Option is A

Step 1: Concept:
Gadolinium (Z=64) is a lanthanide. It has exceptional configuration due to half-filled f-subshell stability.
Step 2: Explanation:
Expected: [Xe] \(4f^8 6s^2\). Actual: [Xe] \(4f^7 5d^1 6s^2\).
Half-filled \(4f^7\) (7 electrons, all unpaired) is extra stable. 5d\(^1\) electron is promoted from 4f.
Step 3: Conclusion:
Thus, Gd = [Xe] \(4f^7 5d^1 6s^2\).