Work out number of atoms instantly with clear inputs, formula shown and shareable results.
A mass is turned into an atom count in two steps: divide by the molar mass to get moles, then multiply by the Avogadro constant to get formula units. Multiplying by the atoms in each formula unit finishes the job, so 18 g of water (1 mol) contains 1.81x10^24 atoms rather than 6.02x10^23.
Moles from mass
moles = mass / molar mass
Atoms
atoms = moles x 6.022e23 x atoms per formula unit
Yes. The molar mass entered is assumed to describe the whole sample, so for a mixture you would work out each component separately.
Set atoms per formula unit to 1 and the atom total becomes the formula-unit total.