What is the ground-state electron configuration of a neutral Iron (Fe) atom (Z = 26)?
[Ar] 4s² 4p⁶
[Ar] 3d⁸
[Ar] 3d⁶ 4s²
[Ar] 3d⁷ 4s¹
📝 Detailed explanation
For Iron (Z=26), electrons fill the 4s orbital first, then the 3d. The configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶, which is simplified to [Ar] 3d⁶ 4s².