Which of the following represents the correct ground-state electron configuration for a Chromium (Cr) atom (Z = 24)?
[Ar] 4s² 3d⁴
[Ar] 3d⁵ 4s¹
[Ar] 4s¹ 4p⁵
[Ar] 3d⁶
📝 Detailed explanation
Chromium is an exception to the Aufbau principle. To achieve the extra stability of a half-filled d-subshell, one electron from the 4s orbital promotes to the 3d orbital, resulting in [Ar] 3d⁵ 4s¹.
