The electronic configuration of the Fe2+ ion, given that iron has atomic number 26, is
- A. [Ar] 3d4 4s2
- B. [Ar] 3d6
- C. [Ar] 3d5 4s1
- D. [Ar] 3d8
Explanation
Neutral iron is [Ar] 3d6 4s2, and forming the two plus ion removes both 4s electrons because 4s lies above 3d once the d subshell is occupied, leaving 3d6. Removing d electrons instead and writing 3d4 4s2 is the classic mistake. Losing one further 3d electron gives the more stable half filled 3d5 arrangement of Fe3+.
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