Derive the electronic configuration of Ce^3+ ion by using Hund's rule.

The correct answer is Option (2) → $[Xe] 4f^1$

Cerium (Ce) has atomic number 58.

Step 1: Electronic configuration of neutral Ce

$\text{Ce} : [Xe]\,4f^1\,5d^1\,6s^2$

Step 2: Formation of $\text{Ce}^{3+}$

• Electrons are removed first from 6s, then 5d, then 4f.
• Remove 3 electrons:
• 2 from 6s
• 1 from 5d

So,

$\text{Ce}^{3+} : [Xe]\,4f^1$

According to Hund’s rule, the single 4f electron remains unpaired.