Question

define: atomic radius (atomic size).

Answer 1

Atomic Radius is defined as the distance between centre of the nucleus to the outermost electron shell

Answer 2

Atom is very small part of a element.

The Atomic radius of a chemical element is a measure of the size of its atoms, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding cloud of electrons.

It is approx 10000 fm.