Radioisotope

             A radioactive isotopes are called radioisotopes. It will produce the radio active naturally or artificially. ( some chemical elements have the unstable nucleus so it will decay to give a stable nucleus.The element decay time some radio activity will produce. This type of isotopes are called radioisotopes.

Atomic Mass

                The mass of an atom of a chemical element weighed by how abundance each isotopes in nature. It is also known as average atomic mass Or atomic weight.

Isotope

           Atoms of an element with the same atomic number and different mass numbers are called isotopes.
Example :
Protium Or Hydrogen . (₁H¹)      
 Deutrium Or Heavy water. (₁H²)

Tritium.    (₁H³)

Mass Number

               The total number of protons and neutrons in an atom is known as mass number. It is represented as the letter ' A '. It is also known as nucleon number.

Example :

                    ¹⁹₉F       ²₁H
* The bigger number 19 is mass number.
* The smaller number 9 is Atomic number.

Atomic Number

              The number of protons in an atom is known as atomic number. ( which means number of protons equal to number of electrons). It is otherwise known as proton number.It id represented as the letter ' Z ' .
Example:
Atomic number of oxygen,  Z = 8
Atomic number of hydrogen, Z = 1
Atomic number of carbon, Z = 6

Hetero-nuclear Diatomic Molecule

                   Diatomic molecules are chemical compounds of two different elements combine to form hetero-nuclear diatomic molecules. It depends on the temperature and pressure.
Example: Carbon monoxide, Hydrogen-fluoride, 

Homo-nuclear Diatomic Molecule

           Chemical compounds of two same elements combine to form a stable homo-nuclear diatomic molecule at standard temperature and pressure.
Example: Hydrogen, Nitrogen, Oxygen.