Question

the chemical reactivity of halogens decreases from top to bottom. Why ?

Answer 1

As we go down the table,The atomic size increases.as the atomic size increases,the elements have less tendency to attract the shared of the electrons in a molecule.Hence the reactivity decreases

Answer 2

Hi friend

Alkali metals have one electron in their respective valence shells.

Thus, reactivity of halogens depends upon their ability to attract electrons.

Since this tendency to gain electrons decreases down the group due to increase in size hence reactivity decreases down the group

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