Question

define shielding effect and discuss why it decreases in a period and increase in a group?​

Answer 1

The shielding effect can be defined as a reduction in the effective nuclear charge on the electron cloud, due to a difference in the attraction forces on the electrons in the atom. It is a special case of electric-field screening.

Down a group, the number of energy levels (n) increases, and so does the distance between the nucleus and the outermost orbital. The increased distance and the increased shielding weaken the nuclear attraction, and so an atom can't attract electrons as strongly.

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