alleryThe electronic configuration of Cr (Z = 24) is:
A[Ar] 3d³ 4s³
B[Ar] 3d⁵ 4s¹
C[Ar] 3d⁶ 4s⁰
D[Ar] 3d⁴ 4s²
Answer & Solution
Correct answer: B. [Ar] 3d⁵ 4s¹
**Cr: [Ar] 3d⁵ 4s¹** (not 3d⁴ 4s²).
The half-filled 3d⁵ + half-filled 4s¹ configuration provides **extra stability** from exchange energy and symmetry.
**Similar exception in Cu:** 3d¹⁰ 4s¹ (not 3d⁹ 4s²).
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