Question

why nucleophilicity increases down the group​

Answer 1

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⚛Nucleophiles:-

Nucleophile means "nucleus loving" which describes the tendency of an electron rich species to be attracted to the positive nuclear charge of an electron poor species, the electrophile .

The nucleophilicity expresses the ability of the nucleophile to react in this fashion.

In general terms this can be appreciated by considering the availability of the electrons in the nucleophile. The more available the electrons, the more nucleophilic the system.

Hence the first step should be to locate the nucleophilic center. At this point we will be considering Nu that contain lone pairs and may be anionic, however the high electron density of a C=C is also a nucleophile.

⚛The more available the electrons, the more nucleophilic the system. ... Within a group in the periodic table, increasing polarisation of the nucleophile as you go down a group enhances the ability to form the new C-X bond and increases the nucleophilicity, so I- > Br- > Cl- > F-

Answer 2

Answer:

The more available the electrons, the more nucleophilic the system. ... Within a group in the periodic table, increasing polarisation of the nucleophile as you go down a group enhances the ability to form the new C-X bond and increases the nucleophilicity, so I- > Br- > Cl- > F-.