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JEE Main 2000 Chemistry question on Atomic Structure

The electronic configuration of an element is 1s2,2s22p6,3s23p63d5,4s11s^2, 2s^2 2p^6, 3s^2 3p^6 3d^5, 4s^1. This represents its
  1. A.
    excited state
  2. B.
    ground state
  3. C.
    cationic form
  4. D.
    anionic form
Show answer and solution

Correct option: B

Solution

This is the ground state electronic configuration of Chromium (Z = 24). Cr adopts the configuration [Ar] 3d⁵ 4s¹ rather than the expected 3d⁴ 4s² because a half-filled d subshell (3d⁵) has extra stability due to exchange energy and symmetrical electron distribution. Since this is the most stable, lowest-energy arrangement for the neutral Cr atom, it represents the ground state.

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