Empirical Formula

A formula that simply gives the ratio of the number of atoms of each element in a compound.
Example: The empirical formula of hydrogen peroxide, H₂O₂, is HO.

A formula that gives the actual numbers of atoms of each element in each molecule of a compound.
Example: The molecular formula of hydrogen peroxide is H₂O₂.

Mole

A mole is a measure of the number of atoms, molecules, or ions there are present. One mole of particles is 6.02 x 10²³ particles (Avogadro's number).

Number of moles = mass in grams / molecular weight

Density

Density = mass / volume