Question

explain the need of term average atomic mass

Answer 1

The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance (the decimal associated with percent of atoms of that element that are of a given isotope). ... An element does not have an absolute atomic mass.

Answer 2

. Isotopes are the atoms of the same elements having same atomic number containing same number of protons and electrons but different no number of neutron hence posses different mass numberis known as average atomic mass.