Answer:
D. Cr
Explanation:
In order to determine which atom has at least one electron in its d orbital, we have to write their theoretical electron configurations.
- ₁₉K 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
- ₂₄Cr 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴
Cr has 4 electrons in d orbitals. Cr belongs to the d-block in the periodic table.
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