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Question
Explain the anomalous behaviour of chromium.
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Solution
- Chromium (Cr) has atomic number 24.
- Its expected electronic configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d4.
- The 3d orbital is less stable, as it is not half-filled.
- Due to inter-electronic repulsion forces, one 4s electron enters into the 3d orbital. This makes the 4s and 3d orbitals half-filled, which gives extra stability, and the electronic configuration of Cr becomes 1s2 2s2 2p6 3s2 3p6 4s1 3d5.
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