Atomicity (chemistry)
Atomicity is the total number of atoms present in one molecule of an element or a substance.
Example
Consider the formation of hydrogen chloride (HCl) from hydrogen (H) and chlorine (Cl). The balanced chemical equation can be written as:
H2 (g) + Cl2 (g) → 2HCl (g)
1 volume + 1 volume → 2 volumes
n molecules + n molecules → 2n molecules ...(One volume of gas contains 'n' molecules.)
1 Molecules +1 Molecules → 2 Molecules ...(Dividing by 'n') OR
½ Molecules + ½ Molecules → 1 Molecules
This suggests that, 1 molecule of Hydrogen Chloride contains 1/2 molecule of hydrogen and 1/2 molecule of Chlorine. i.e. Atomicity of Hydrogen and Chlorine is 2 respectively. Also atomicity of HCl is 2.
f gases
A molecule which contains only one atom is called monatomic (inert gases), A molecule which contains two atoms is called diatomic (oxygen, nitric oxide, hydrogen, etc.) and A molecule containing three atoms is called a triatomic or tetra-atomic oleculele (ozone, sulphur dioxide, carbon dioxide,etc.)and A molecule containing more than 3 atoms are known as a polyatomic ions (phosphate,sulphur,etc.)