(a) How are the following related?

(i) Number of valence electrons of different elements in the same group.

(ii) Number of shells of elements in the same period.

(b) How do the following change?

(i) Number of shells of elements as we go down a group.

(ii) Number of valence electrons of elements on moving from left to right in a period.

(iii)Atomic radius in moving from left to right along a period.

(iv) Atomic size down a group.

(a) (i) In the same group, all the elements have same number of valence electrons.

Group number of an element (up to 2 valence electrons) = no. of valence electrons

Group n. of element (more than 2 valence electrons) = 10+ Valence electrons.

(i) Elements present in the same period have same number of shells.

Period number of an element = no. of shells in an atom

(b) (i) As we go down the group, no. of shells increases at every step.

(ii) As we go from left to right in a period, no. of valence electrons of an element increases from period 1 to period 8.

(iii)When we move from left to right in a period, there is increase in the large positive charge on the nucleus. As a result, the forces of attraction between the nucleus and the electrons increases. This led to increase in the atomic radius of the elements from left to right in a period.

(iv)The atomic size increases down the group due to increase in a shell at every step.