What is a periodic property? How the following properties vary in a group and in a period? Explain
(a) IP.

Explanation

The repetition of similar physical and chemical propertes of elements at regular intervals with increasing atomc number is called periodic property or periodicity.
(a) Trends of I.P : As we go from left to rigth in a period, atomic radius gradually decreases. As result of which the nuclear attractions on the valence electrons gradually increases. So, the energy required to remove the outer electrons gradually increases. In other words, as we go from left to right in a period, the I.P. value increase.
As we go from top to bottom in a group, atomic radius gradually increases. As a result of which the nuclear attraction on the valence electrons gradually decreases. So, hte energy required to remove the outer electrons gradually decreases. In other electrons gradually decreases. In other words, in a group the I.P. values gradually decrease from top to bottom.