Question

what is mean by Bulkier a given nucleophile ,lower its nucleophilicity?

Answer 1

Also as Electronegativity increases, nucleophilicity decreases because More the Electronegativity — More tightly it is held — Less ability to donate it's pair of electrons. Steric Effect: The bulkier a given nucleophile is, the slower the rate of its reactions [and therefore the lower its nucleophilicity].