In comparison of ferrous salts, ferric salts are :

Ferric salts (Fe³⁺) are more stable in comparison of ferrous salts(Fe²⁺).As half filled 3d⁵ configuration is more stable. ${\mathrm{Fe}}^{3+}\to [\mathrm{Ar}{]}^{18}3{\mathrm{d}}^5,{\mathrm{Fe}}^{2+}\to [\mathrm{Ar}{]}^{18}3{\mathrm{d}}^6$.