$F{e}^{3+}$ ion is more stable than  $F{e}^{2+}$ ion because ……………..? 

$F{e}^{2+}$ has a smaller size than that of  $F{e}^{+3}$

configuration of  $F{e}^{2+}$ is  $3d^6$ while $F{e}^{+3}$  is  $3d^5$

$F{e}^{3+}$ ion is coloured hence more stable

more the charge on the atom, more is its stability