Edexcel GCSE Chemistry key terms

A model in which an atom has a tiny, positively charged central nucleus and electrons outside it.

A proton or neutron; both are particles found in an atomic nucleus.

A monomer from which DNA polymer chains are made; DNA contains four different types.

The central part of an atom, containing protons and usually neutrons.

A system that can exchange matter with its surroundings.

The approximate power of ten representing the scale of a quantity; quantities differing by one order of magnitude differ by a factor of about 10.

Rock containing enough of a metal or metal compound for extraction to be considered worthwhile.

An electron in the outermost occupied shell of an atom; it is the electron involved when a Group 1 atom forms a positive ion.

The occupied electron shell furthest from an atom's nucleus; its electrons are involved in chemical reactions.

An electron in the outermost occupied electron shell of an atom; these electrons can take part in bonding.

The difference between the energy absorbed in breaking reactant bonds and the energy released when product bonds form.

The net result of the energy required to break bonds in the reactants and the energy released when bonds form in the products.

The gain of oxygen by a substance during a chemical reaction.

Gases containing nitrogen chemically combined with oxygen, formed when nitrogen and oxygen react at high temperatures; they are often represented collectively as $\mathrm{NO_x}$.

Able to cause or intensify burning by supporting oxidation.

A gas that supports combustion and makes a glowing splint relight.

A pair of elements whose order does not follow increasing relative atomic mass because the chemically appropriate order is the reverse.

A method of separating soluble substances as a solvent carries them through paper at different speeds.

A model that explains the properties of matter using the arrangement, movement and energy of its particles.

One part in every hundred, calculated by dividing the relevant part by the whole and multiplying by 100.

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

The fraction of a whole expressed out of 100; for oxygen in air, it can be estimated from the volume of oxygen removed divided by the initial volume of air.

The actual yield expressed as a percentage of the theoretical yield.

A horizontal row of elements in the periodic table.

A pattern in which similar chemical properties recur at regular intervals when elements are placed in a suitable order.

A chart of the elements arranged in order of increasing atomic number, with vertical groups and horizontal periods.

Equipment worn to reduce exposure to a hazard, such as eye protection or protective gloves selected for a particular task.