Question

What is atomicity? How are molecules classified based on atomicity?

Answer 1

Atomicity is the number of the atom that combines to form a molecule.
Molecules are classified based on the number of constituents atoms like monoatomic, diatomic, and polyatomic.
Monoatomic molecules contain only one atom. Helium, Neon, Krypton are examples of monoatomic molecules.
Some atoms can not exist independently so they exist as a combination of two atoms, which are known as diatomic molecules. Oxygen, nitrogen, hydrogen are a few examples of diatomic molecules.
The last category is polyatomic molecules where molecules contain three or more atoms. The sulphur molecule contains 8 atoms of a sulphur atom and phosphorous molecules contain 4 phosphorous atoms, which are examples of polyatomic molecules.