Avogadro's Number
Definition and meaning of Avogadro's Number in chemistry.
Avogadro's number is the quantity 6.022 × 10²³, representing the number of atoms, molecules, or particles in one mole of a substance. This fundamental constant allows chemists to convert between atomic/molecular scale and macroscopic quantities.
In more detail
Named after Italian physicist Amedeo Avogadro, this number elegantly bridges the gap between the atomic world and the macroscopic quantities we measure in the laboratory. One mole of any substance contains exactly this many particles, whether it is a gas, liquid, or solid. The constant is essential for stoichiometry, chemical equations, and understanding the relationship between atomic mass units and gram-based measurements. It enables chemists to count enormous numbers of particles indirectly by simply measuring mass on a balance.
Key facts
| Symbol | Nₐ |
|---|---|
| Value | 6.022 × 10²³ particles/mol |
| Named after | Amedeo Avogadro (1776–1856) |
| Field | Physical Chemistry |
If you have 12 grams of carbon-12, you have exactly 6.022 × 10²³ carbon atoms (one mole). If you have 18 grams of water (H2O), you have 6.022 × 10²³ water molecules.
Frequently asked questions
Why is Avogadro's number important?
It allows chemists to count enormous numbers of atoms or molecules by simply weighing a sample. This is fundamental to all quantitative chemical work.
Does Avogadro's number apply to all substances?
Yes, one mole of any substance, solid, liquid, or gas, contains exactly 6.022 × 10²³ particles, regardless of the identity of the substance.