Question

The correct electronic configuration of chromium (Z = 24) is

(A) \([Ar]3d^54s^1\)

(B) \([Ar]3d^44s^2\)

(C) \([Ar]3d^64s^0\)

(D) \([Ar]3d^44s^14p^1\) 

Answer 1

Correct option is (A) \([Ar]3d^54s^1\)

• Element Chromium(Cr) has an atomic number 24.
• According to the Aufbau series,
  1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7p < 8s
• The electronic configuration should be: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴.
• However, the actual electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵.
• This occurs because the half-filled configuration 3d⁵ is more stable.
• Hence, the electron configuration of chromium (z = 24) is [Ar]3d⁵4s¹.