question_answer

How many unpaired electrons are present in the central metal ion of \[{{[CoC{{l}_{4}}]}^{2-}}\] [Orissa JEE 2005]

A) 3

B) 4

C) 5

D) 2

Correct Answer: A

Solution :

\[_{27}Co\to [Ar]3{{d}^{7}}4{{s}^{2}}\] \[C{{o}^{2+}}\to 3{{d}^{7}}4{{s}^{0}}\] Number of unpaired electrons = 3.