Question

Explain why the similarity of chemical properties of groups of elements is due to their electron configurations ?

could someone help me please ..

Answer 1

the chemical properties of an element have to do with how they react/bond with other elements. these reactions/bonds affect the electron shells, in fact, the outer electron shells (not the nucleus). if they affected the nucleus they'd be nuclear reactions.
as such, a group has the same (or nearly the same) outer electron shells which react/bond giving rise to similar properties for the group.

Answer 2

thank you so much :)