d$^5$ (high-spin)

d$^4$ (high-spin)

d$^6$ (low-spin)

d$^3$

$NH_3$ is a strong field ligand and causes pairing of the d-electrons.

$NH_3$ is a weak field ligand and does not cause pairing of the d-electrons.

$Co^{3+}$ has a $d^{10}$ configuration.

The complex has a tetrahedral geometry.

${\rm{C}}{{\rm{u}}^{2 + }} + 4{\rm{N}}{{\rm{H}}_3}\leftrightharpoons{\left[ {{\rm{Cu}}{{\left( {{\rm{N}}{{\rm{H}}_3}} \right)}_4}} \right]^{2 + }}{\rm{\;\;}};\left( {K = 4.5 imes {{10}^{11}}} \right)$

${\rm{C}}{{\rm{u}}^2} + 4{\rm{CN}}\leftrightharpoons{\left[ {{\rm{Cu}}{{\left( {{\rm{CN}}} \right)}_4}} \right]^{2 - }}{\rm{\;}};\left( {K = 2.0 imes {{10}^{27}}} \right)$

${\rm{C}}{{\rm{u}}^{2 + }} + 2{\rm{en}}\leftrightharpoons{\left[ {{\rm{Cu}}{{\left( {{\rm{en}}} \right)}_2}} \right]^{2 + }}{\rm{\;}};{\rm{\;\;}}\left( {K = 3.0 imes {{10}^{15}}} \right)$

${\rm{C}}{{\rm{u}}^{2 + }} + 4{{\rm{H}}_2}{\rm{O}}\leftrightharpoons{\left[ {{\rm{Cu}}{{\left( {{{\rm{H}}_2}{\rm{O}}} \right)}_4}} \right]^{2 + }}{\rm{\;}};\left( {K = 9.5 imes {{10}^8}} \right)$

[Cr(H₂O)₆]²⁺

[Cr(CN)₆]⁴⁻

[Fe(CN)₆]⁴⁻

[Co(NH₃)₆]³⁺

$ext{I}^-$

$ext{Br}^-$

$ext{H}_2ext{O}$

$ext{CN}^-$

[Co(CN)₆]³⁻

[Co(NH₃)₆]³⁺

[CoBr₆]³⁻

[Co(H₂O)₆]³⁺

The oxidation state of the metal ion

The nature of the ligands

The geometry of the complex

The size of the metal cation

${\left[ {{\rm{Ni}}{{\left( {{\rm{CN}}} \right)}_4}} \right]^{2 - }}$

${\left[ {{\rm{Cr}}{{\left( {{\rm{N}}{{\rm{H}}_3}} \right)}_6}} \right]^{3 + }}$

${\left[ {{\rm{Fe}}{{\left( {{{\rm{H}}_2}{\rm{O}}} \right)}_6}} \right]^{2 + }}$

${\left[ {{\rm{Ni}}{{\left( {{{\rm{H}}_2}{\rm{O}}} \right)}_6}} \right]^{2 + }}$

Completely filled $d -$orbitals

Vacant $d -$orbitals

$d - d$ transition

None of the above

0 BM

1.73 BM

2.83 BM

4.9 BM

$[\{\rm Co\}(\{\rm CN\}_6]^{3-} < [\{\rm Co\}(\{\rm en\})_3]^{3+} < [\{\rm Co\}(\{\rm NH\}_3)_6]^{3+} < [\{\rm Co\}(\{\rm H\}_2\{\rm O\})_6]^{3+}$

$[\{\rm Co\}(\{\rm H\}_2\{\rm O\})_6]^{3+} < [\{\rm Co\}(\{\rm NH\}_3)_6]^{3+} < [\{\rm Co\}(\{\rm en\})_3]^{3+} < [\{\rm Co\}(\{\rm CN\}_6]^{3-}$

$[\{\rm Co\}(\{\rm en\})_3]^{3+} < [\{\rm Co\}(\{\rm CN\}_6]^{3-} < [\{\rm Co\}(\{\rm H\}_2\{\rm O\})_6]^{3+} < [\{\rm Co\}(\{\rm NH\}_3)_6]^{3+}$

$[\{\rm Co\}(\{\rm NH\}_3)_6]^{3+} < [\{\rm Co\}(\{\rm H\}_2\{\rm O\})_6]^{3+} < [\{\rm Co\}(\{\rm CN\}_6]^{3-} < [\{\rm Co\}(\{\rm en\})_3]^{3+}$