Concept:Gold (\(Au\)) is in Group 11, similar to Copper and Silver. Elements in this group exhibit anomalous electron configurations to achieve a highly stable, fully filled \(d\)-subshell.
Solution:- Gold has an atomic number \(Z = 79\). The core is Xenon (\(Z = 54\)).
- The \(4f\) subshell fills completely with 14 electrons: \(54 + 14 = 68\).
- There are 11 valence electrons left for the \(5d\) and \(6s\) orbitals.
- Instead of the expected \(6s^2 \; 5d^9\), one electron shifts from \(6s\) to \(5d\) to achieve the extra stability of a completely filled \(d\)-subshell (\(d^{10}\)).
- The final configuration is \([Xe] \; 4f^{14} \; 5d^{10} \; 6s^1\).
Why other options are incorrect:- Option B represents the expected but incorrect \(d^9\) configuration.
- Option D exceeds the total electron count (80 electrons instead of 79).
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