Question

How is the size of an atom indicated

Answer 1

The atomic size depends on the number of shells. An increase in the number of shells increases the size of an atom because the distance between the outermost shell and the nucleus increases.
OR
size of an atom is indicated by the no. of shell's present in it.

Answer 2

the atomic size depends upon the number of shells. the number of shells is depend upon the number of electrons present. if there would be more number of electrons present, there will be more number of shells, as per electronic communication,and the size of the atom will be bigger and vice versa