In VOSO4 oxidation state of vanadium is +4. =[Ar]3d34s2 V4+=[Ar]3d14s0 Therefore, it is paramagnetic. In K2Cr2O7 oxidation state of Cr=+6, unpaired electron =0 In (NH4)2[TiCl6] oxidation state of Ti=+4, unpaired electron =0 In K3[Cu(CN)4] oxidation state of Cu=+1, unpaired electron =0 In K2Cr2O7,(NH4)2[TiCl6] and K3[Cu(CN)4] in coloured but diamagnetic but VOSO4 paramagnetic and coloured.