atoms + elements

• Atom


  Representation of each element by a chemical symbol
• There are about 100 different elements, all of which are shown in the periodic table
• Element


  A substance made up of only one type of atom
• All atoms of a particular element have the same number of protons
• Atoms of different elements have different numbers of protons
• Periodic table


  Organised by atomic number, also known as proton number
• Compound


  Contains two or more elements chemically combined in fixed proportions
• Compound formation


  Elements undergoing chemical reactions
• Chemical bonds


  Atoms of different elements held together
• Compounds can only be separated into elements by chemical reactions
• Chemical reaction


  Involves the formation of one or more new substances and often involves a detectable energy change
• Chemical formula


  Describes the atoms present within a compound
• Chemical formula


  • Carbon dioxide, CO2
  • Water, H2O
• Molecule


  The smallest particle of a compound that has all of the physical and chemical properties of that compound