AQA GCSE Chemistry key terms

The power of ten that describes the approximate scale of a value.

A rock containing enough of a metal or metal compound for the metal to be extracted.

The pencil line on which samples are placed at the start of paper chromatography.

The occupied energy level furthest from the nucleus.

An electron in the highest occupied energy level of an atom; these electrons have the greatest influence on its chemical behaviour.

The electrons in the highest occupied energy level of an atom; these are involved in chemical reactions.

The difference between the energy levels of the products and the reactants.

The loss of electrons by a substance.

The charge associated with an element in a compound or ion, often shown by a Roman numeral in a transition-metal compound's name.

A general name for several compounds of nitrogen and oxygen, often written as NOₓ.

A substance that causes another substance to be oxidised; chlorine acts as an oxidising agent when it bleaches coloured substances.

A model that explains matter as particles and chemical reactions as rearrangements of atoms.

Tiny solid particles suspended in the air, including soot or carbon particles.

The independent assessment of scientific work by other experts in the same field before publication.

The –CO–NH– connection between neighbouring amino-acid residues in a polypeptide chain.

The proportion of a compound's total mass contributed by a specified element, expressed as a percentage.

The amount of product actually obtained expressed as a percentage of the maximum theoretical amount.

A horizontal row of the periodic table; for the first 20 elements, its number equals the number of occupied electron shells.

A repeating pattern in the physical or chemical properties of elements when they are arranged by atomic number.

A systematic arrangement of elements that places elements with recurring, similar properties into groups.

A numerical measure related to the hydrogen ion concentration of a solution; lower pH means a higher hydrogen ion concentration.

Mined material containing phosphate compounds; it must be treated to make its phosphorus more available to plants.

The process in which algae and plants use light energy to make glucose from carbon dioxide and water, releasing oxygen.

An electronic sensor used to measure the pH of a solution and give a numerical reading.

A numbered scale, usually from 0 to 14, that measures the acidity or alkalinity of a solution.

A biological extraction method in which plants absorb metal compounds, after which the plants are harvested and burned to produce metal-containing ash.

A piece of apparatus used to transfer one accurately measured, fixed volume of solution.