In the complex ${\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ the electronic configuration of ${\mathrm{Fe}}^{2+}$ is $\left[\mathrm{Ar}\right]3{\mathrm{d}}^6$. ${\mathrm{H}}_2\mathrm{O}$ is a weak ligand. Hence, the crystal filed splitting can be shown as follows,

In the complex ${\left[\mathrm{Mn}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ the electronic configuration of ${\mathrm{Mn}}^{2+}$ is $\left[\mathrm{Ar}\right]3{\mathrm{d}}^5$. ${\mathrm{H}}_2\mathrm{O}$ is a weak ligand. Hence, the crystal filed splitting can be shown as follows,

In the complex ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}$ the electronic configuration of ${\mathrm{Fe}}^{3+}$ is $\left[\mathrm{Ar}\right]3{\mathrm{d}}^6$. ${\mathrm{NH}}_3$ is a strong filed ligand. Hence, the crystal filed splitting can be shown as follows,

 

 

In the complex ${\left[{\mathrm{FeCl}}_4\right]}^{-}$ the electronic configuration of ${\mathrm{Fe}}^{3+}$ is $\left[\mathrm{Ar}\right]3{\mathrm{d}}^5$. ${\mathrm{Cl}}^{-}$ is a weak ligand. Hence, the crystal filed splitting can be shown as follows,

 

 

 

In the complex ${\left[{\mathrm{CoCl}}_4\right]}^{2-}$ the electronic configuration of ${\mathrm{Co}}^{2+}$ is $\left[\mathrm{Ar}\right]3{\mathrm{d}}^7$. ${\mathrm{Cl}}^{-}$ is a weak ligand. Hence, the crystal filed splitting can be shown as follows,