Question

Difference between atomic number and mass number.

Answer 1

The atomic number is the number of electrons present in an atom. It is equal to the number of protons in a neutral atom. It is denoted by symbol $z$.

The mass number, also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus.

It is represented by A.

$\therefore A-Z$ represents the number of neutrons.