Question

What is a diatomic molecule?

Answer 1

Hint: Atomicity is known as the total number of atoms present in a molecule. On the basis of atomicity, molecules are classified as: Monoatomic molecule, diatomic molecule, Triatomic molecule and Polyatomic molecule.

Complete answer:
A molecule which consists of two atoms is called a diatomic molecule. At room temperature all diatomic molecules are gases.
The substances that have crystalline or other atomic arrangements at room temperature become diatomic at higher temperatures. Compounds such as carbon monoxide and nitric oxide have diatomic molecules. The seven diatomic elements are Nitrogen, Hydrogen, Fluorine, Oxygen, Iodine, Bromine and Chlorine. Hydrogen is the most universally abundant diatomic molecule.
All diatomic molecules are linear and are characterised by a single parameter that is the bond length or bond distance between the two atoms.
The diatomic nitrogen atom has triple bond, diatomic oxygen atom has double bond while the diatomic hydrogen, fluorine, iodine, bromine and chlorine atoms have single bonds.
Diatomic molecules are further divided as homonuclear diatomic molecules and heteronuclear diatomic molecules.
A Homonuclear diatomic molecule consists of two combined atoms of the same substance. Example: $N_2,O_2$.
Heteronuclear diatomic molecule consists of two atoms of different elements. Example:$HCl,HF$

Note:
We can use simple ways to determine the atomicity of any element. It is determined as a ratio of molecular mass and atomic mass. For example, using the oxygen molecule, the molecular mass is $16\times 2=32$ while the atomic mass is 16. If we divide the two, we get atomicity as $2$ .