Question

What is the difference between $2\mathrm{O}$ and ${\mathrm{O}}_2$?

Answer 1

Atom :

• An atom is the smallest constituent unit of matter possessing the properties of an element.
• Example : Sodium atom ($\mathrm{Na}$), Carbon atom ($\mathrm{C}$) etc.

$2\mathrm{O}$ represents two atoms of Oxygen. These atoms of Oxygen are unstable and can readily react to form molecules.

Molecule :

• A molecule is a group of two or more than two atoms chemically combined.
• Example : Molecule of Nitrogen (${\mathrm{N}}_2$), molecule of Hydrogen (${\mathrm{H}}_2$)etc.

${\mathrm{O}}_2$ represents a molecule of Oxygen where two atoms of Oxygen have combined chemically. ${\mathrm{O}}_2$ molecule is stable.