Question

how atomic size and valency of an element varies in a group and a period​

Answer 1

Answer:

atomic size increases in group from up to down and decrease period wise

valency is same for same groups

valency first increases and then decreases ( period wise)

Answer 2

Answer:

atomic size increases as we move down the group because of increase of no of shells

while atomic size decrease while moving from left to right in a period because of increase in effective nuclear charge

valency of a group remains constant therefore while moving down the group valency remains same because of same no of valence electrons in outermost shell

valency of a period first increases and then decreases