Question

Largest atomic size is:
A. C
B. N
C. F
D. O

Answer 1

Hint: We know that the atom is generally one of the smallest units of the chemical matter, which is commonly used for making the elements. The atoms are very small around $100$ picometers. In general, across a period from left to right, the atomic size decreases due to the increased effective nuclear charge and within a group from top to bottom the atomic size increases due to the successive addition of energy shells.

Complete step by step answer:
The atomic size is usually explained by the distance or space between the center of the atoms’ nucleus and its outermost shell. The atomic radius is the shortest distance between the nucleus and the outer shell of that atom. The atomic radius in the group from moving top to bottom gradually increases, and it decreases from moving left to the right in a period. The nuclear size of carbon is more significant than nitrogen, fluorine, and oxygen. The one proton has a more major consequence than one electron; thus, the electrons are drawn towards the atomic nucleus, causing a smaller radius. The carbon atom has the greater atomic size among all the other choices; they are nitrogen, fluorine, and oxygen.

Therefore, the correct choice for this given question is A.

Note:
The atomic size decreases from moving left to right across the period, and it gradually decreases from moving top to right in the group.