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Electron configuration of d orbital

Chemistry Level 2

Which of the following elements is not consistent with its electron configuration at ground state?

\[\text{Cu: [Ar]}3d^{9}4s^{2}\] \[\text{Mn: [Ar]}3d^{5}4s^{2}\] \[\text{Co: [Ar]}3d^{7}4s^{2}\] \[\text{Cr: [Ar]}3d^{5}4s^{1}\]

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by Krishna Singh

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