Avogadro's Number

Avogadro's number tells you how many individual particles are in 1 mole of a substance. Because a mole is defined as a fixed counting unit, multiplying the number of moles by 6.022 × 10^23 converts a chemical amount into an actual particle count. This works for atoms, molecules, ions, or formula units, as long as you count the correct kind of particle.

Use this formula when a question asks for the number of particles in a given amount of substance, such as atoms in iron, molecules in water, or ions in a salt. It is also useful when converting between moles and particle counts in stoichiometry and lab calculations.

• Using grams instead of moles without converting first
• Forgetting that N_A gives particles per mole, not per gram
• Counting the wrong particle type, such as atoms instead of molecules