[Olympiad] How many unpaired electrons are present in a high-spin Fe²⁺ ion (Z=26) in an octahedral crystal field?
0
2
4
6
📝 Detailed explanation
Fe²⁺ has a 3d⁶ configuration. In a high-spin octahedral field, electrons fill t2g and eg levels following Hund's rule: 3 electrons in t2g (up), 2 in eg (up), then the 6th electron pairs in t2g (down). Result: 4 unpaired electrons.
