Key terms & definitions

A proposed description of an atom that can be changed when new evidence is found.

An explanation of an atom’s structure that can be tested and changed when new evidence is found.

A representation used to explain observations and make predictions about how atoms behave.

The number of protons in the nucleus of an atom; it identifies the element.

The number of protons in a nucleus, written at the lower left of a nuclide symbol; it determines the element.

The number of protons in an atom's nucleus. In a neutral atom, it also equals the number of electrons.

The number of protons in a nucleus, written as $Z$. It identifies the element.

The approximate distance from the centre of an atom to the extent of its electron cloud.

An approximate distance from the centre of an atom to the outer extent of its electron region.

The structure of an atom, comprising a central nucleus containing protons and neutrons, with electrons occupying energy levels around it.

A historical measure of an element’s atomic mass relative to that of another atom; it corresponds broadly to what is now called relative atomic mass.

A historical name for relative atomic mass: the weighted mean mass of an element’s atoms compared with one-twelfth of the mass of a carbon-12 atom. It accounts for the masses and abundances of its isotopes.

A comparison showing the relative numbers of different atoms, written in the same order as their element symbols.

Making amends for wrongdoing through actions that repair harm.

The restoration of the relationship between God and humanity through Jesus Christ’s sacrifice.

A molecule that transfers chemical energy for cellular processes such as active transport, movement and the synthesis of larger molecules.

Adenosine triphosphate: a molecule that transfers energy for processes within cells.

A political group in central southern Britain whose rulers developed trading and political relationships with Rome; Verica was one of its kings.

A valve between an atrium and a ventricle that prevents blood flowing back into the atrium when the ventricle contracts.

An upper chamber of the heart that receives blood returning to the heart.

An upper chamber of the heart that receives blood.

The main central hall of a Roman house, often containing a rainwater pool beneath an opening in the roof.

An upper chamber of the heart that receives blood and pumps it into a ventricle. The heart has a right atrium and a left atrium.

An act of extreme cruelty, such as the massacre of civilians or prisoners.

Clinging to people, possessions or experiences as though they could provide permanent satisfaction.

A dependence on possessions that makes someone unwilling to give them up, even when they obstruct commitment to God.

A measure of performance in eight GCSE-level qualifications in England. English and mathematics receive extra weighting, giving a maximum score of 90.

A difference in educational results between groups of pupils, measured using the same indicator.

A reduction in the intensity of radiation as it passes through matter.

The countryside and territory surrounding the city of Athens.