Question

atomic mass number is a whole number give scientific reason

Answer 1

$\bf\huge\color{red}\mathbb{Hello\:User....}$

Atomic mass number ( A ) is always a whole number this is because :--
● The atomic mass number is simply the sum of number of protons and neutrons in the nucleus of that atom. Since the number of protons and neutrons can not be present in fractions that's why the atomic mass number is always a whole number.

$\bf\huge\color{blue}\mathbb{BUT}$

●The atomic mass number of Chlorine ( Cl ) is 35.5 or 35. This us because of its isotopes.
We can call it as an exception.