question_answer

The number of unpaired electrons in me complex ion \[{{[Co{{F}_{6}}]}^{3-}}\] is:                                   [AIPMT 2003]

(Atomic number \[Co=27\])

A) 4

B) zero

C) 2

D) 3

Correct Answer: A

Solution :

[a] In complex ion \[{{[Co{{F}_{6}}]}^{3-}}\,,\,Co\] is present at +3 oxidation state

\[_{27}Co=1{{s}^{2}},2{{s}^{2}}\,2{{p}^{6}},\,3{{s}^{2}}3{{p}^{6}}\,3{{d}^{7}},4{{s}^{2}}\]

\[C{{o}^{3+}}=1{{s}^{2}},2{{s}^{2}}\,2{{p}^{6}},3{{s}^{2}}3{{p}^{6}}\,3{{d}^{6}}\]

Thus, the number of unpaired electrons in 3d sub-shell of \[{{[Co{{F}_{6}}]}^{3-}}\] is 4.