Atom: An atom is the defining structure of an element. It cannot be broken by any chemical means.
Electron: An electron is a negatively charged component of an atom. Electrons surround the atoms nucleus.
Proton: A component of the nucleus with a mass number of 1 and a charge of +1.
Neutron: A component of the nucleus with a mass defined as 1, and a charge of 0.
Nucleus: The centre of an atom. Composed of neutrons and protons, and possessing most of the mass.
Atomic number: The number of protons in the nucleus of an atom. It determines the chemical properties of an element and its place in the periodic table.
Mass number: The total number of protons and neutrons in the nucleus.
Element: A class of substances that cannot be separated into simpler substances by chemical means. Compound: A substance composed of two or more elements.
Ion: An electrically charged atom, or group of atoms, formed by the loss or gain of one or more electrons.
Cation: A positively charged atom, or group of atoms, caused by an atom, or group of atoms, losing one or more electrons.
Anion: A negatively charged atom or group of atoms caused by an atom, or group of atoms, gaining one or more electrons.
Monatomic ion: An ion consisting of one atom.
Polyatomic ion: An ion consisting of two or more atoms.
Chemical formula: Letters used to represent the individual elements in a compound.
Reactant: A substance that takes part in, and undergoes change during a reaction.
Product: A substance produced by a chemical reaction.
Word equation: An equation in which words are used to show both the reactants and products of a chemical reaction.
Chemical equation: An equation in which chemical formulae are used to show both the reactants and products of a chemical reaction.
Activation energy: The least amount of energy required to start a chemical reaction.
Catalyst: A substance that changes the rate of a chemical reaction but is not used up in the reaction.
Collision theory: In order for a chemical reaction to occur, two or more particles must collide with sufficient energy and at the correct orientation.
Concentration: The measure of how much of a substance is mixed with another substance.
Kinetic energy: Energy that an object possesses by being in motion.
Particle: One of the extremely small constituents of matter. Things such as atoms, molecules, and ions are particles.
Particle theory: Matter is made up of tiny particles which are constantly moving.
Product: A substance, or substances, produced by a chemical reaction.
Reactant: A substance that takes part in and undergoes change during a reaction.
Reaction rate: A measure of how fast reactants become products during a chemical reaction.
Surface area: The total area of exposed surfaces.
Acid: A chemical substance that neutralizes bases, dissolves some metals. and turns litmus red. They have a pH <7.
Base: A base is any substance that can accept hydronium ions and neutralise acids. They have a pH in solution of >7
Alkali: A base that is soluble in water.
Concentrated: Lots of solute particles dissolved in a small amount of solvent.
Dilute: A small number of solute particles dissolved in a large amount of solvent.
Neutralisation: The absorption of hydronium ions by bases so that pH moves towards
Salt: Salts are ionic compounds formed from the neutralisation reaction of an acid and a base.
Dissociation: The separation of ions or molecules when placed in water
pH Scale: A logarithmic scale showing the concentration of hydrogen ions, and therefore the relative concentration of acids and bases. (pH stands for Power of Hydrogen Ions.)