Question

Assertion $[ CoF_6]^{3-}$ is paramagnetic. Reason $Co^{3+}$ has $3d^6$ outer electronic configuration. The unpaired electrons do not pair up because of weak field provided by $F^-$ .

• A. Both Assertion and Reason are true and Reason is the correct explanation of assertion.
• B. Both Assertion and Reason are true and Reason is not the correct explanation of Assertion.
• C. Assertion is true but Reason is false.
• D. Both Assertion and Reasonl are false.

Answer 1

Answer: (A)

In complex$[CoF_6]^{3-}$
Oxidation number of Co= +3
Electronic configuration of
$Co^{3+} = 1s^2, 2s^2, 2p^6, 3s^2 3p^6, 3d^6$
In $Co^{3+}$
In $Co^{3+}$ number of unpaired electrons is four, and $F^-$ is the ligand of weak field. Hence, it does not paired up electrons of d-orbital.
So, In$[CoF_6)]^{3-}$
So, $[ CoF_6 ]^{3-}$ is paramagnetic.
$Co^{3+}$ has $3d^6$ outer electronic configuration, but four unpaired electrons do not pair up because of weak field provided by $F^-.$