Def

• Alkali metals


  The elements in Group 1 of the periodic table
• Atom


  The smallest part of an element that can exist. All substances are made up of atoms
• Atomic nucleus


  Positively charged object composed of protons and neutrons at the centre of every atom with one or more electrons orbiting it
• Atomic number


  The number of protons in the nucleus
• Chromatography


  A separation technique used to separate a mixture of chemicals by distributing the components between two phases
• Compound


  A substance made up of two or more types of atoms chemically combined together
• Crystallisation


  A separation technique used to produce solid crystals from a solution by evaporating the solvent
• Displacement


  A chemical reaction in which a more reactive element displaces a less reactive element from its compound
• Electron


  Negatively charged subatomic particle which orbit the nucleus at various energy levels. Very small relative mass (negligible)
• Electron shell


  Different energy levels in atoms occupied by electrons
• Element


  A substance made up of only one type of atom
• Filtration


  A separation technique used to separate solids from liquids
• Fractional distillation


  A method of separating a mixture of substances according to their different boiling points
• Group (periodic table)


  The columns of the periodic table represent different groups of elements. Elements with similar properties are in the same group
• Halogens


  The elements in Group 7 of the periodic table
• Ion


  An atom or molecule with an electric charge due to the loss or gain of electrons
• Isotope


  Atoms of the same element with the same number of protons but a different number of neutrons
• Mass number


  The total number of protons and neutrons in the nucleus
• Metals


  Elements that react to form positive ions. Found to the left and towards the bottom of the periodic table
• Mixture


  A mixture consists of two or more elements or compounds not chemically combined together
• Neutron


  Neutral subatomic particle present in the nucleus of the atom. Relative mass of 1
• Noble gases


  The elements in Group 0 of the periodic table
• Non-metals


  Elements that react to form negative ions. Found towards the right and top of the periodic table
• Nuclear model


  The nuclear atomic model stated that the mass was concentrated at the centre of the atom and that the nucleus was charged
• Periodic table


  Table of elements arranged in order of atomic number and such that elements with similar properties are in the same column (group)
• Plum pudding model


  Atomic model devised after the discovery of the electron. The model suggests the atom is a ball of positive charge with negative electrons scattered through it
• Proton


  Positively charged subatomic particle present in the nucleus of the atom. Relative mass of 1
• Relative atomic mass


  An average value that takes account of the abundance of the isotopes of the element
• Simple distillation


  A procedure by which two liquids with different boiling points can be separated
• Transition metals


  The collection of metallic elements in the middle of the periodic table