Chemistry 1

• Aqueous solution: the mixture made by adding a soluble substance to water
• Atom: the smallest part of an element that can still be recognised as that element
• Atomic number: the number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number
• Balanced symbol equation: a symbol equation in which there are equal numbers of each type of atom on either side of the equation
• Biofuel: fuel made from animal or plant products
• Chromatography: the process whereby small amounts of dissolved substances are separated by running a solvent along a material such as absorbent paper
• Compound: a substance made when two or more elements are chemically bonded together
• Electron: a tiny particle with a negative charge. Electrons orbit the nucleus of atoms or ions in shells
• Electronic structure: a set of numbers to show the arrangement of electrons in their shells (or energy levels)
• Element: a substance made up of only one type of atom. An element cannot be broken down chemically into any simpler substance
• Group: all the elements in the columns (labelled 1 to 7 and 0) in the periodic table
• Ion: a charged particle produced by the loss or gain of electrons
• Isotope: atoms that have the same number of protons but different number of neutrons, i.e., they have the same atomic number but different mass numbers
• Law of conservation of mass: the total mass of the products formed in a reaction is equal to the total mass of the reactants
• Mass number: the number of protons plus neutrons in the nucleus of an atom
• Neutron: a dense particle found in the nucleus of an atom. It is electrically neutral, carrying no charge
• Noble gases: the very unreactive gases found in Group 0 of the periodic table. Their atoms have very stable electronic structures
• Nucleus (of an atom): the very small and dense central part of an atom that contains protons and neutrons
• Periodic table: an arrangement of elements in the order of their atomic numbers, forming groups and periods
• Product: a substance made as a result of a chemical reaction
• Proton: a tiny positive particle found inside the nucleus of an atom
• Reactant: a substance we start with before a chemical reaction takes place
• Shell: an area in an atom, around its nucleus, where electrons are found
• State symbol: the abbreviations used in balanced symbol equations to show if reactants and products are solid (s), liquid (l), gas (g) or dissolved in water (aq)
• Symbol equation: an equation that helps you see how much of each substance is involved in a chemical reaction by showing the chemical symbols and formulae of all the reactants and products involved
• Word equation: a way of describing what happens in a chemical reaction by showing the names of all reactants and the products they form