JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Atomic Structure

The electronic configuration of Pt (atomic number 78) is:

(A) $[Xe] 4 f^{14} 5 d^{9} 6 s^{1}$ ✓ Correct
(B) $[Kr] 4 f^{14} 5 d^{10}$
(C) $[Xe] 4 f^{14} 5 d^{10}$
(D) $[Xe] 4 f^{14} 5 d^{8} 6 s^{2}$

Answer: (A)

Solution

Platinum (Pt, Z=78) is a d-block element that exhibits an exceptional electronic configuration for extra stability.

The expected configuration would be

[Xe] 4 f^{14} 5 d^{8} 6 s^{2}

, but due to the extra stability associated with a nearly-filled d-subshell, one electron from the 6s orbital is promoted to the 5d orbital.

The actual configuration is:

[Xe] 4 f^{14} 5 d^{9} 6 s^{1}

Answer: (A)

JEE Main · 2022 · 29 Jun 2022 · Shift 1 · Single correct option

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