Term | Definition |
Atom | The smallest part of an element that can still be recognised as an element. |
Atomic Number | The number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number. |
Compound | A substance made when two or more elements are chemically bonded together. For example water, H2O, is a compound made from hydrogen and oxygen. |
Covalent Bond | The attraction between two atoms that share one, or more, pairs of electrons. |
Covalent Bonding | The attraction between two atoms that share one, or more, pairs of electrons. |
Delocalised Electron | Bonding electron that is no longer associated with any one particular atom. |
Dot and Cross Diagram | A drawing to show the arrangement of the outer shell electrons only of the atoms or ions in a substance. |
Double Bond | A covalent bond made by the sharing of two pairs of electrons. |
Electron | A tiny particle with a negative charge. Electrons orbit the nucleus in atoms or ions. |
Electronic Structure | A set of numbers to show the arrangement of electrons in their shells or energy levels. E.g. the electronic structure of a potassium atom is 2,8,8,1. |
Element | A substance made up of only one type of atom. An element can not be broken down chemically into any simpler substance. |
Energy Level (or Shell) | An area in an atom, around its nucleus, where the electrons are found. |
Shell (or Energy Level) | An area in an atom, around its nucleus, where the electrons are found. |
Gas | A state of matter. |
Inert | Unreactive. |
Ion | A charged particle formed by the loss or gain of electrons. |
Ionic Bond | The electrostatic force of attraction between positively and negatively charged ions. |
Ionic Bonding | The electrostatic force of attraction between positively and negatively charged ions. |
Liquid | A state of matter. |
Mass Number | The number of protons plus neutrons in the nucleus of an atom. |
Mixture | When some elements or compounds are mixed together and intermingle but do not react together. (i.e. no new substance is made). A mixture is not a pure substance. |
Molecule | A group of atoms bonded together, e.g. PCl3. |
Neutron | A dense particle found in the nucleus of an atom. It is electrically neutral, carrying no charge. |
Nucleus ( of an atom) | The very small and dense central part of an atom which contains protons and neutrons. |
Product | A substance made as a result of a chemical reaction. |
Proton | A tiny positive particle found in the nucleus of an atom. |
Reactant | A substance we start with before a chemical reaction takes place. |
Solid | A state of matter. |
State Symbol | The abbreviations used in balanced symbol equations to show to show if reactants or products are solids (s), liquids (l), gases (g) or dissolved in water (aq) |
Symbol Equation | A balanced chemical equation showing the formula of each reactant and product in the reaction. E.g. H2 + Cl2 = 2HCl |