question_answer

Which of the following has the maximum number of unpaired 'd' electrons?

A) \[Z{{n}^{2+}}\]                                

B) \[F{{e}^{2+}}\]

C) \[N{{i}^{3+}}\]                                 

D) \[C{{u}^{+}}\]

Correct Answer: B

Solution :

\[Zn\,\,(30)=[Ar]\,\,3{{d}^{10}},4{{s}^{2}}\]          \[Z{{n}^{2+}}=[Ar]\,\,3{{d}^{10}}\] (no unpaired electron) \[Fe(26)=[Ar]\,3{{d}^{6}},4{{s}^{2}}\]    \[F{{e}^{2+}}=[Ar]\,\,3{{d}^{6}}\] (four unpaired d electrons)                 \[Ni(28)=[Ar]\,\,3{{d}^{8}},\,4{{s}^{2}}\]   \[N{{i}^{3+}}=[Ar]\,\,3{{d}^{7}}\] (three unpaired d electrons)                 \[Cu\,\,(29)=[Ar]\,\,3{{d}^{10}},\,4{{s}^{1}}\]      \[C{{u}^{+}}[Ar]\,3{{d}^{10}}\] (no unpaired electron)