How do atomic radius generally vary in a period and in a group for s-and `p-`block elements ? How do you explain the variation?

Explanation

The atomic size decreases as we move from left to right in a period. This is because when we move along a period the nuclear charge increases and therefore, the attraction of the nucleus for the outer electrons increases and hence the atomic size decreases. Within a group, the atomic size increases down the group. This is because of addition of a new energy shell at each succeeding element while the number of valence electrons remain the same. For detail, refer Text.