On moving down a group, the basicity \& nucleophilicity are inversely related, i.e. nucleophilicity increases while basicity decreases. i.e RS⊖ is more nucleophilic but less basic than RO⊖. This opposite behaviour is because of the fact that basicity and nucleophilicity depends upon different factors. Basicity is directly related to the strength of the H -element bond, while nucleophilicity is indirectly related to the electronegativity of the atom to which proton is attached.