What is monoatomic

Monoatomic means the basic unit consists of one single atom only. It can be used to describe molecules or ions.

For example:

1. Molecules - All noble gases consist of single atoms or monoatomic molecules. Oxygen, on the other hand, exist as O2 molecules which consist of 2 Oxygen atoms. It is described as di-atomic molecule. Water molecules (H2O) each consist of 3 atoms (2 Hydrogen atoms + 1 Oxygen atom) and is know as tri-atomic molecule. Molecules that consist of more than 1 atom are collectively known as poly-atomic molecules.

2. Ions - Each sodium ion (Na+) is made up from 1 sodium atom and is described as monoatomic ion. On the other hand, each nitrate ion (NO3−) is made up from more than 1 atoms (1 Nitrogen atom + 3 Oxygen atoms) and is known as poly-atomic ion.

monoatomic is mention the type of covalent bonding.
They only have one pair of covalent bonding
For example : group VII elements .
Eg. Fluorine always exist as F2