What is a periodic property? How the following properties vary in a group and in a period? Expain
(a) Atomic radius.

Explanation

Recurrence of similar properties of elements at definite regular intervals with increasing atomic number i.e., according to their electronic configurations is known as periodicity. Any property which is periodic in nature is called periodic property.
Atomic radius: The atomic radius decreases from left to right in a period. With an increase in the atomic number in a period the nuclear charge increase. As a result the effective nuclear charge over the outermost electrons increases, due to this the orbitals are pulled closer to the nucleus causing in a decrease in the atomic radius.
The atomic radius increases from top to the bottom in a group because-with an increase in teh atomic number th electrons are added to new shells resulting an increase in the number of inner shells. Hence atomic, radius increases from top to bottom in a group. The atomic radius increases from top to the bottom in a group because-with an increase in the atomic number the electrons are added to new shells resulting an increase in the number of inner shells. Hence, atomic radius increases from top to bottom in a group.