Atoms, Molecules, and Stoichiometry Flashcards

Flashcards covering key concepts from the lecture notes on atoms, molecules, and stoichiometry.

Relative atomic mass (Ar)

The mass of an atom relative to one twelfth of the mass of an atom of carbon-12.

Unified atomic mass

One-twelfth of the mass of a carbon-12 isotope (1 u = 1.66 x 10-27 kg)

Isotopes

Atoms of the same element with a different number of neutrons.

Relative isotopic mass

The mass of an atom of an isotope relative to one twelfth of the mass of an atom of carbon-12.

Relative molecular mass (Mr)

The mass of a molecule relative to one twelfth of the mass of an atom of carbon-12.

Relative formula mass (Mr)

Used for compounds containing ions; calculated the same way as relative molecular mass.

Avogadro constant (NA or L)

The number of particles equivalent to the relative atomic mass or molecular mass of a substance (6.02 x 1023 mol-1).

Mole (mol)

The mass of a substance containing the same number of fundamental units as there are atoms in exactly 12.00 g of 12C.

Empirical formula

The simplest whole number ratio of the elements present in one molecule or formula unit of the compound.

Molecular formula

The formula that shows the number and type of each atom in a molecule.

Water of crystallisation

When some compounds can form crystals which have water as part of their structure.

Hydrated compound

A compound that contains water of crystallisation.

Anhydrous compound

A compound which doesn’t contain water of crystallisation.