Elements + compounds: Atomic structure and the periodic table: Chemistry: GCSE (9:1)

• Atom


  Smallest part of an element
• Element


  A pure substance made of only one kind of atom

  
• Compound

  A substance made up of atoms of two or more different elements joined by chemical bonds

  
• Mixture


  A combination of two or more different substances that are not joined by chemical bonds

  
• Chemical symbol


  A one or two letter representation of an element

  
• Number of elements

  118

  
• Chemical reaction


  the formation of a new chemical substance

  
• Periodic table


  A chart of the elements showing the repeating pattern of their properties

  
• Property

  a description of a substance (e.g. soft/dense/shiny/reactive)

  
• Molecule


  A group of atoms bonded together (can be the same type of atom, or different types of atom).
• Separation of compounds

  requires a chemical reaction to break the bonds between atoms.
• Formula of an element

  Has a single capital letter (e.g. O or Na)
• Formula of a compound

  Has more than one capital letter, and tells you the ratio of the elements in a compound. (e.g. CaO has a 1:1 ratio of calcium to oxygen)
• Word equation


  A way of writing out what happens in a chemical reaction using the names of the substances involved.
• Symbol equation


  A way of writing out what happens in a chemical reaction using the symbols that represent the substances involved.
• Reactants

  The substance(s) changed in a chemical reaction

  
• Products

  The new substance(s) formed in a chemical reaction