Concept: Unpaired electrons are determined by applying Hund's Rule to the outermost valence subshell.
Formula: None required.
Solution: - Let's analyze the options:
- \( Z=6 \) (Carbon): \( 1s^2, 2s^2, 2p^2 \). The two \(2p\) electrons go into separate orbitals (2 unpaired).
- \( Z=14 \) (Silicon): \( [Ne] 3s^2, 3p^2 \). Similar to Carbon, it has 2 unpaired electrons.
- \( Z=22 \) (Titanium): \( [Ar] 4s^2, 3d^2 \). The two \(3d\) electrons are unpaired (2 unpaired).
- \( Z=26 \) (Iron): \( [Ar] 4s^2, 3d^6 \). The \(3d\) subshell has 5 orbitals. Placing 6 electrons means 1 orbital is paired and the remaining 4 orbitals hold exactly 1 electron each.
- Therefore, Iron (\(Z=26\)) has exactly 4 unpaired electrons.
Why other options are incorrect: They all possess only 2 unpaired electrons in their ground state.
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