The Mole

Different atoms have different masses.

1g of carbon has far fewer atoms than 1g of hydrogen atoms.

Chemists need a method of quantifying atoms.

We use a quantity called the amount of substance which is measured in moles.

One mole contains 6.02 x 10²³ particles.

The relative atomic mass is the mass of one mole of that element’s atoms.

The relative molecular mass is the mass of one mole of molecules

• 1 mole of oxygen contains 6.02 x 10²³ oxygen atoms.
• 1 mole of carbon molecules contains 6.02 x10²³ carbon molecules.
• 1 mole of electrons contains 6.02 x 10²³ electrons.

Avogadro's Constant

Avogadro's constant, L, or N_A is the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by one mole (mol).

Avogadro's constant is 6.02 × 10²³ mol^-1

Molar Mass

Molar mass, M, is the mass per mole of a substance.

The units of molar mass are g/mol.

For atoms of an element it is simply the relative atomic mass in g/mol

For sodium this is 23 g/mol.

For compounds it is the relative atomic masses of each atom in the formula added together.

The Molar Mass of CH₄ = C + (H x 4) = 12 + (1 x 4) = 16 g/mol.