Question

What does “Homonuclear” and “Diatomic” mean?

Answer 1

Homo is the term that is used to define the same kind of substance. When we have to tell the number of atoms in the molecule we can use the terms like mono-, di-, tri-, tetra-, Penta-, etc. in the prefix.

Complete answer:
We know that molecules and compounds are made up of elements. There are two types of molecules based on the types of elements present in the molecule, i.e., when the atoms are of the same and when the atoms are of different elements. The terms given are homonuclear and heteronuclear molecules.
Homonuclear means the molecules in which atoms are present of the same element, for example, ${{O}_{2}}$ is homonuclear because there are two atoms in ${{O}_{2}}$ and both of them are of the oxygen atom. Other examples are ${{N}_{2}}$, ${{S}_{8}}$, ${{P}_{4}}$, etc.
When we have to tell the number of atoms in the molecule we can use the terms like mono-, di-, tri-, tetra-, Penta-, etc. in the prefix.
So, diatomic is the term used to define the molecules in which there are two atoms present; they can be either of the same elements or different elements. The examples of diatomic molecules are ${{O}_{2}}$, ${{N}_{2}}$, CO, NO, HCl, KBr, etc.
We can also say that ${{O}_{2}}$, ${{N}_{2}}$, etc are the example of homonuclear molecules, and CO, NO, HCl, KBr, etc are the examples of heteronuclear diatomic molecules.

Note:
${{S}_{8}}$ is an example of homonuclear octa-atomic molecules, ${{P}_{4}}$ is an example of homonuclear tetra-atomic molecules. Most compounds are the example of heteronuclear molecules.