Avogadro constant
The number of atoms or molecules in one mole of a substance: N_A = 6.02 × 10²³ mol⁻¹. It is a fundamental constant linking macroscopic and microscopic scales of matter.
Formula
Nₐ = 6.02 × 10²³ mol⁻¹
Real World
A 12 g sample of pure carbon-12 contains exactly one mole — 6.02 × 10²³ atoms — a fact used by particle accelerator teams at CERN to calculate beam intensities.
Exam Focus
When finding the number of molecules, multiply moles by Nₐ; a common error is dividing instead — check units to catch this.
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