How do the following change ?
(a) Number of shells of elements as we go down a group.
(b) Number of valence electrons of elements on moving from, left to right in a period.
(c ) Atomic radius in moving from left to right along a period.
(d) Atomic size down a group.

Explanation

(a) Number of shells of elements goes on increasing down the group.
(b) Number of valence electrons of elements goes on increasing on moving from left to right in a period eg. Lithium has 1, beryllium has 2, boron has 3, carbon has 4, nitrogen has 5, oxygen has 6, fluorine has 7 and Neon has 8 valence electrons.
(c ) Atomic radius goes on decreasing in moving from left to right along a period.
(d) atomic size goes on increasing down a group.