Question

Define atomic size of an element.

Atomic radii of some elements like C, Li, N, O, B and Be are 77, 152, 74, 66, 88 and 111 pm respectively.

Rearrange them in decreasing order of their atomic radii.

Name the elements which have largest and the smallest size respectively.

Give reason for the change in atomic radius as you move from left to right in a period.

Answer 1

atomic radius is defined as the distance from the centre of the nucleus to the outermost orbit

Li,Be,B,C,N&O

Li has the largest size & O has the smallest size

across a period the atomic radius decreases because the number of electrons increases and due attraction between the negatively charged electrons and the positively charged protons in the nucleus increases therefore the size decreases.