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

  • A. [Ar] 3d4 4s2
  • B. [Ar] 3d5 4s1
  • C. [Ar] 3d6 4s0
  • D. [Ar] 3d3 4s3

Explanation

Chromium promotes one 4s electron into the 3d subshell because a half filled d5 configuration alongside a half filled 4s is more stable than d4 with a full 4s. Copper does the same thing to reach a full d10. The 4s subshell can never hold three electrons, which rules out the last option outright.

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