Arrangement the following elements in increasing order of their atomic radii
(a) Li, Be, F, N
(b) Cl, At, Br, I

Explanation

(a) All the elements belong to the same period (second). The atomic size or radius decreases along a period. Therefore, increasing order of atomic radii is : `F lt N lt Be lt Li`
(b) The listed elements are present in group 17 (halogen family). The atomic size or radius increases down a group. Therefore, the correct increasing order of atomic radii is : `Cl lt Br lt I lt At`.