We use moles (mol) to measure the amount of a substance. Specifically, one mole of a substance contains the same number of particles as one mole of another substance.
The Avogadro constant is the number of particles in one mole of a substance. These particles can be atoms, molecules, ions or electrons. The Avogadro constant is written in standard form, as 6.02 × 10²³. But, this value is equal to 602,000,000,000,000,000,000,000.
The mass of 6.02 × 10²³ particles of a substance is the same as the substance’s relative atomic or relative formula mass in grams.
For example, since the relative atomic mass of carbon is 12, 1 mol of carbon will weigh exactly 12 grams. In other words, 1 mol is also the amount of substance that contains the same number of particles as there are atoms in 12.0 g of carbon-12.
Particles in a substance can be calculated by both the Avogadro constant, and the amount of substance in moles:
Calculate the number of atoms in 1 mol of sodium oxide (Na2O)
Calculate the number of carbon dioxide (CO2) molecules in 0.8 mol of carbon dioxide.