Distinguish between the following pairs . Justify.
`3O_(2) " and " 2O_(3), 3O" and " O_(3)`

Explanation

`3O_(2)` represents 3 molecules of oxygen. This is because `O_(2)` is the formula of oxygen and one molecule of oxygen is made up of 2 atoms and `2O_(3)` represents 2 molecules of ozone. This is because `O_(3)` is the formula of ozone and one molecule of ozone is made up of 3 atoms.
3O represents 3 atoms of oxygen as .O. is the symbol of oxygen. `O_(3)` represents one molecule of ozone.
The number in the subscript represents the number of atoms in a single molecule. This number written as the coefficient represents the number of atoms or molecules as the case may be.