What is meant by atomicity 1 How many different types of molecules are known on the basis of atomicity?

The number of atoms present in one molecule of the substance is called its atomicity. Depending on the number of atoms present in a molecule, the following types of molecules are known:
(i) Monoatomic molecules : The noble gases exist as single atoms and, therefore, their molecules are monoatomic.
(ii) Diatomic molecules : The molecules consisting of two atoms, e.g., O2, N2, Cl2, H2, Br2,I2, etc.
(iii) Triatomic molecules : The molecules consisting of three atoms, e.g., 03 (Ozone molecule).
(iv) Tetratomic molecules : The molecules consisting of four atoms, e.g., P4 (Phosphorus molecule).
(v) Polyatomic molecules : The molecules consisting of more than four atoms, e-g; S8 (Sulphur molecule).
Note: All of the above types are the molecules of an element, which means one, two or more atoms of the same element existing as one species in the free state.