A Level Chemistry Definitions

Atoms of the same element with different numbers of neutrons and different mass numbers.

The mass of an isotope compared with 1/12 of the mass of an atom of carbon-12.

The weighted mean mass of an atom compared with 1/12 of the mass of an atom of carbon-12.

The amount of substance that contains 6.02 x 10^23 (Avogadro’s number) particles.

The simplest whole number ratio of atoms of each element present in a compound.

The number and type of atoms of each element present in a molecule.

A compound that doesn’t contain any water of crystallisation.

A compound that contains water(s) of crystallisation.

Water molecules that form an essential part of a compound’s crystalline structure.

A substance that releases H+ ions in aqueous solution.

A substance that releases OH- ions in aqueous solution.

An acid that partially dissociates in solution.

An acid that fully dissociates in solution.

A region around the nucleus that can hold up to 2 electrons in opposite spin.

Electrostatic attraction between oppositely charged ions.

Electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

A covalent bond where both of the shared electrons are donated by one of the bonding atoms.

The ability of an atom to attract a shared pair of electrons in a covalent bond.

Repeating trends in physical/chemical properties across periods of the periodic table.

The amount of energy required to remove one mole of electrons from one mole of gaseous atoms in order to form one mole of gaseous 1+ ions.

Electrostatic attraction between metal cations and delocalised electrons.

Oxidation and reduction of the same element in a reaction.

More energy is released forming bonds than energy taken in breaking bonds.

More energy is taken in breaking bonds than energy released forming bonds.