Class 11 NEET Chemistry Classification Of Elements And Periodicity In Properties

In going from left to right across a period in the periodic table, the basicity (i.e. proton affinity) decreases as the electronegativity of the atom possessing the lone pair of electrons increases. Hence basicity of NH2−is higher than F− In moving down a group, as the atomic mass increases, basicity decreases. Hence F− is more basics than I− and HO− is more basics than HS−.Hence among the given ionic species, NH2− has maximum proton affinity.