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