Arrange giving reason the following elements in the increasing order of their atomic size:
a) Be, O, F (Given that they belong to 2nd, 8th, and 9th groups and 2nd period respectively)
b) I, CI, F (Given that they belong to 5th, 3rd, and 2nd period respectively in the same group)
c) Mg, N, P (Given that Mg and P belong to 2nd and 15th group respectively of 3rd period and N belongs to 15th group of 2nd period)

Explanation

a) `F < O < Be`, since atomic size decreases from left to right in a period.
b] `F < Cl < 1`, since atomic size increases down a group.
c)  `N < P < Mg`, because Mg, being in lower group, has the largest atomic size. P has a larger size compared to N as it lies below N in the same group.