Q88 / 200 · NEET 2003 · Chemistry

The number of unpaired electrons in the complex ion $\left[\mathrm{CoF}_6\right]^{3-}$ is: (Atomic no. : $\mathrm{Co}=27$ )

  • A
    2
  • B
    3
  • Correct answer
    C
    4
  • D
    Zero

Solution

\(\mathrm{Co}(\mathrm{Z}=27)\) has observed electronic configuration \([\mathrm{Ar}] 3 \mathrm{~d}^7 4 \mathrm{~s}^2 . \mathrm{Co}^{3+}\) has electronic configuration \([\mathrm{Ar}] 3 \mathrm{~d}^6 4 \mathrm{~s}^0 \cdot\left[\mathrm{CoF}_6\right]^{3-}\) is a high spin complex and contains 4 unpaired electrons.

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

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