Question

Why is atomic mass of an atom defined as relative atomic mass??

Answer 1

Relative atomic mass of an element is the ratio between the average mass of its isotopes to 1/12th part of the mass of a carbon - 12 atom. It is denoted as Ar . It is otherwise called " Standard Atomic Weight "

Relative Atomic mass

( Ar ) = Average mass of the isotopes of the element / 1/12th of the mass of one carbon - 12 atom