Question

explain why the tendency to gain electrons change as go down in a group?

Answer 1

When we go down the group we move to higher elements ie they have more Number of shells. So now they can store more Number of electrons. The tendency to gain electrons depends on the repulsion the coming electron gets to come into the orbit. As there are more free shells now so distance from the nucleus of the coming electrons increases and less repulsion is what the electron feels and so it is easy to get into the orbital..!
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