Q77 / 160 · JIPMER 2005 · Chemistry

The incorrect configuration is

  • A
    $\mathrm{K}=[\mathrm{Ar}] 4 s^1$
  • B
    $\mathrm{Cr}=[\mathrm{Ar}] 3 d^5 4 s^1$
  • Correct answer
    C
    $\mathrm{Cr}=[\mathrm{Ar}] 3 d^4 4 s^1$
  • D
    $\mathrm{Cu}=[\mathrm{Ar}] 3 d^{10} 4 s^1$

Solution

The correct configurations of $\mathrm{K}, \mathrm{Cu}$ and Cr are $[\mathrm{Ar}] 4 s^1,[\mathrm{Ar}] 3 d^{10} 4 s^1,[\mathrm{Ar}] 3 d^5 4 s^1$ respectively. As half filled and completely filled d orbitals are more stable, hence in case of Cr and Cu one electron shifts from $4 s$ orbital to $3 d$ orbital to give them stable electronic configuration.

Hence, the correct answer is option: 'C'.

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