Chem paper 1

• 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
• Coarse particles


  Coarse particles (PM10) have diameters between 1 x 10-5 m and 2.5 x 10-6 m. They are often referred to as dust
• Conductor


  A material which contains charged particles which are free to move to carry electrical or thermal energy
• Covalent bond


  A shared pair of electrons between two non-metals
• Diamond


  A giant covalent structure which is made up of carbon atoms each of which form four covalent bonds with four other carbon atoms
• Electrostatic forces


  The strong forces of attraction between oppositely charged ions
• Empirical formula


  The smallest whole number ratio of atoms of each element in a compound
• Fine particles


  Fine particles (PM2.5) have diameters between 100 and 2500 nm (1 x 10-7 m and 2.5 x 10-6 m)
• Fullerenes


  Fullerenes are molecules of carbon atoms with hollow shapes. The structures are based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms
• Gas


  The state of matter where the particles have the most energy. The particles in a gas are relatively spread out and move randomly in all directions
• Graphene


  A single layer of graphite with properties that make it useful in electronics and composites