How many unpaired electrons are present in \(_{26}Fe^{3+}\)?
A.
4
B.
2
C.
3
D.
5
Correct answer is D
There are 5 unpaired electrons present in \(_{26}Fe^{3+}\).
The atomic number of iron is 26, so it has 26 electrons. When iron loses 3 electrons to form \(Fe^{3+}\), it loses 2 from the s orbital and 1 from the d orbital. This leaves 5 unpaired electrons in the d orbital.
The electron configuration of \(Fe^{3+}\) is [Ar]3d5. The 5 d electrons are all unpaired because Hund's rule states that electrons will occupy degenerate orbitals singly before they pair up. This is because unpaired electrons have a lower energy than paired electrons.
