Chemistry key terms

A memory aid for redox in terms of electrons: Oxidation Is Loss of electrons; Reduction Is Gain of electrons.

A system that can exchange matter with its surroundings.

A value at which the measured outcome is greatest or most favourable under the stated criterion.

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.

A compound based on carbon atoms, usually with carbon bonded to hydrogen and sometimes to other elements.

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

The result or event whose relationship with a factor is being investigated.

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 highest occupied electron energy level in an atom; its electrons are involved in chemical reactions and bonding.

The occupied energy level furthest from the nucleus.

An electron in the highest occupied energy level of an atom.

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

A result that differs noticeably from the pattern formed by the other results.

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

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

Loss of electrons by a substance during a reaction.

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 compound containing oxygen and at least one other element.

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

Able to cause or intensify burning by supporting oxidation.

A substance that causes another substance to be oxidised.

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

A gas made of three oxygen atoms per molecule, O₃, which forms an ultraviolet-absorbing layer in the upper atmosphere.

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 a mixture of soluble substances as a solvent carries them at different rates through a stationary phase.

An error in reading a scale caused by viewing it from an angle rather than directly at the level of the reading.

An atom, molecule or ion represented as one unit in a particle model; its meaning depends on the substance being modelled.

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

Tiny solid particles or liquid droplets suspended in the atmosphere; soot is one example.