+2 and +3 oxidation state of transition elements

+2 and +3 oxidation state of transition elementsAcross the periodStability of +2 oxidation stateStability of +3 oxidation state

Reason of nuclear charge binds d subshell electrons more strongly. difficulty of removing the third electron from d orbitals.elementTi VCrMnFeCoNiCuEo M2+/M (V)-1.63-1.18-0.91-1.18-0.44-0.28-0.25+0.34Eo M3+/M2+(V)-0.37-0.26-0.41+1.49+0.77+1.82--O2+4H++4e- =2H202H++2e-=H2Stabilities of transition elements can be predicted based on S.E.P.E0 of M2+/M and M3+/M2+ as compared to Eo=0V (for acidic solution) and Eo =+1.23V(in air)-ve E0 value of M3+/M2+ indicates higher oxidation state (+3) is more stable (eg. Ti, V &Cr)+ve E0 value of M3+/M2+ indicates lower oxidation state (+2) is more stable in aqueous solution.(eg. Mn & Co) ( note: same as pg 44&45)Fe2+ is stable in absence of O2. Fe2+ is unstable and will be further oxidised to Fe3+ in the presence of O2 .+2 ions start as strong reducing agent whereas +3 ions start stable and become more oxidising across the period.Strong oxidising agent such as Co3+ can react with water spontaneously releasing O2 .4Co3+ + 2H2O4Co2+ +O2 + 4H+