0ATOMIC SIZE:- atomic radius(size) is defined as the distance between the nucleus of an atom and the outer most shell of an atom.
TREND OF ATOMIC SIZE IN PERIODIC TABLE:
A) In the period from left to right atomic size goes on decreases because of-
1) Nuclear charge increases from left to right.
2) The number of shells will be the same.
Hence attraction force between nucleus and valence electrons increases, so atomic size decreases.
B) In the same group from top to bottom atomic size increases because-
1) The number of shells goes on increases from top to bottom.
2) Nuclear charge increases but due to the screening effect, its impact is less.
