Find the reason for the follwing:
i) Size of the atom decrease from left to right across a period.
ii) Size of atom increases from top to bottom in a group

Explanation

a) On movinf from left to right along a period the nuclear charge increases. The force of attraction on the outermost electrons increases and consequently the size of the atom decreases.
b) As we move from top to bottom along a group in the periodic table, size of the atom increases as there is an increase in the number of shells.