The question requires understanding the anomalous electronic configurations of chromium and copper, which occur due to the stability associated with half-filled and fully-filled d orbitals.
The expected electronic configuration, following the Aufbau principle, usually involves filling the 4s orbital before the 3d orbital. However, chromium and copper show deviations from this rule.
For chromium (atomic number 24), the expected configuration would be \([Ar]4s^2 3d^4\). But, chromium exhibits an anomalous behavior, where it achieves a more stable configuration by promoting one electron from the 4s orbital to the 3d orbital to achieve a half-filled d orbital, leading to the configuration \([Ar]4s^1 3d^5\).
For copper (atomic number 29), the expected configuration would be \([Ar]4s^2 3d^9\). Instead, copper also shows a similar deviation where it promotes one electron from the 4s orbital to the 3d orbital to achieve a fully filled d orbital, resulting in the configuration \([Ar]4s^1 3d^{10}\).
Both chromium and copper achieve extra stability due to a half-filled or fully filled 3d subshell, respectively. Such configurations exist because half-filled and fully filled orbitals provide added stability due to symmetric distribution of electrons and exchange energy.
Thus, the correct electronic configurations for chromium and copper are:
Chromium: \([Ar]4s^1 3d^5\)
Copper: \([Ar]4s^1 3d^{10}\)
Therefore, the correct answer is: \([Ar]4s^1 3d^5\) and \([Ar]4s^1 3d^{10}\).
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