Concept:Evaluate the \(d\)-subshell configurations to see which element has 1 electron in every \(d\)-orbital (all unpaired, \(d^5\)) and which element has 2 electrons in every \(d\)-orbital (all paired, \(d^{10}\)).
Solution:- Chromium (\(Cr\)): Anomalous configuration is \(3d^5 \; 4s^1\). The 5 electrons in the \(3d\) subshell are distributed singly across all 5 orbitals (Hund's Rule). Thus, it has all unpaired d-orbitals.
- Copper (\(Cu\)): Anomalous configuration is \(3d^{10} \; 4s^1\). The 10 electrons perfectly fill the 5 \(d\)-orbitals, meaning every orbital has a pair. Thus, it has all paired d-orbitals.
- Therefore, the pair \(Cr\) and \(Cu\) perfectly satisfies the condition.
Why other options are incorrect:- Zn: Has all paired d-orbitals (\(3d^{10}\)), but is paired with Cu, which also has all paired d-orbitals.
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