Explanation

(a)
Electronic configuration of $Co^{2 +}$ ion
(a)
$\ \ \ \ \ \ \ \ \ \ \ \ 3d$ $4s^{0}$ $3p$
[table] ⥮ | $\mathbf{\upharpoonleft}$ | $\mathbf{\upharpoonleft}$ | $\mathbf{\upharpoonleft}$ | $\mathbf{\upharpoonleft}$ | | | | | | [/table]
$\left\lbrack CoF_{6} \right\rbrack^{3 -}$ ion $\ \ \ \ \ \ \ \ \ \ \ 3d$
[table] ⥮ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ [/table]
$\$
[image:9_image256.emf]
$\ F^{-}$ is a weak ligand. It cannot pair up electrons with d-subshell and forms outer orbital octahedral complex.
(b) $\left\lbrack Co\left( {NH}_{3} \right)_{6} \right\rbrack^{3 +}$ ion
[image:9_image257.emf]
$4d$
[table] | | | | [/table]
(c) $\left\lbrack Fe(CN)_{6} \right\rbrack^{3 +}$ ion
[image:9_image258.emf]
$4d$
[table] | | | | [/table]
(d) $\left\lbrack Cr\left( {NH}_{3} \right)_{6} \right\rbrack^{3 +}\ ion$
[image:9_image258.emf]
$4d$
[table] | | | | [/table]
$NH_{3}\ and\ CN^{-}$ are strong ligands. So, they form their inner orbital complex.