Question

please explain why electron affinity increases across a period and decreases down a family. Also explain why the same trend holds for ionization energy.

Answer 1

ionization energy : it is defined as the amount of energy is needed to remove an electron from outer most shell

in group : we know that in the group from top to bottom atomic size increases becuase for every new element an extra shell is added.

so the outer most electron is far way from the neucleous . so we can easily remove that electron becuase of less attraction towards center. so less amount of energy is need to remove electron in this case

in period

in the period form left to right atomic size decreases this means electrons are much attracted by nucleous . so we cannot remove outermost electron easily .

so in period less amount of energy is need