What is Avogadro's number?
Avogadro's number (Nₐ) is the number of particles (atoms, molecules, ions, etc.) in exactly one mole of a substance:
Nₐ = 6.02214076 × 10²³ mol⁻¹
This means 1 mole of any substance contains 6.022 × 10²³ particles — whether atoms of iron, molecules of water, or ions of sodium.
How to use
Number of particles = Moles × Nₐ
Example: 2 moles of H₂O = 2 × 6.022 × 10²³ = 1.204 × 10²⁴ molecules of water.