AP Chemistryhardmcq1 pt
What is the ground-state electron configuration of the Fe³⁺ ion (iron, Z = 26)?
A.[Ar] 3d5
B.[Ar] 3d4
C.[Ar] 4s2 3d3
D.[Ar] 3d6
Explanation
Core Concept
Neutral iron is [Ar] 4s² 3d⁶, and transition-metal ions lose their 4s electrons before any 3d electron. Removing three electrons (two 4s, then one 3d) leaves five 3d electrons, written [Ar] 3d⁵. The resulting half-filled d subshell gains extra exchange-energy stability, which is why Fe³⁺ is so common.
Correct Answer
A[Ar] 3d5
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