Relationship Between Atomic Number, Mass Number and Istope

* For Example :   In Carbon-12 and Carbon-14,
¹²₆C                                                          ¹⁴₆C
Neutron - 6                                             Neutron - 8
Proton    - 6                                             Proton    - 6
Electron - 6                                              Electron - 6
Carbon-12 and carbon-14 have same atomic number and different mass number. It's known as isotopes.

* A number of proton in an atom is known as atomic number. Carbon-12 and carbon-14 both of them ontain 6 protons so that the atomic number is 6.
                 Z = 6
Z ==> Atomic number.

*    In carbon-12 , the mass number is 12 and the atomic number is 6. Mass number is bigger than the atomic number.Mass number is equal to the total number of protons and neutrons.