Chemistry Y9 Essential Formula

• Some Formulae

  • water H2O
  • sulphuric acid H2SO4
  • carbon dioxide CO2
  • nitric acid HNO3
  • sulphur dioxide SO2
  • hydrochloric acid HCl
  • sodium hydroxide NaOH
  • ammonia NH3
  • hydrogen peroxide H2O2
  • calcium carbonate CaCO3
• Diatomic Elements

  • H2
  • N2
  • O2
  • F2
  • Cl2
  • Br2
  • I2
• No other elements are diatomic
• Some Common Reactions

  1. metal + acid --> salt + hydrogen

  2. metal oxide + acid --> salt + water

  3. metal hydroxide + acid --> salt + water

  4. metal carbonate + acid --> salt + water + carbon dioxide

  5. ammonia + acid --> ammonium salt

  6. Group I metal (e.g. sodium) + water --> metal hydroxide + hydrogen
• Sulphuric acid makes sulphate salts. Nitric acid makes nitrate salts. Hydrochloric acid makes chloride salts.
• Reactions of elements with other elements

  • Reaction of an element with chlorine makes a chloride
  • Reaction of an element with bromine makes a bromide
  • Reaction of an element with iodine makes an iodide
  • Reaction of an element with oxygen makes an oxide
  • Reaction of an element with sulphur makes a sulphide
  • Reaction of an element with nitrogen makes a nitride
• Some Ions

  • sulphate SO42−
  • ammonium NH4+
  • nitrate NO3−
  • Lead ion Pb2+
  • carbonate CO32−
  • hydrogen ion H+
  • hydroxide OH−
  • Silver ion Ag+
  • Zinc ion Zn2+
• Some Valencies


  • group I 1
  • group II 2
  • group III 3
  • group IV 4
  • group V 3
  • group VI 2
  • group VII 1
  • group 0 0
  • Zinc = 2
  • Silver = 1
  • Hydrogen = 1
• For other elements, the valency should be given in Roman numerals, in brackets, in the name of the compound, e.g. iron(III) oxide
• Transition metal compounds


  Usually coloured
• Compounds which do not contain a transition metal


  Usually white or colourless
• Acidic solutions


  Contain H+ ions, and have a pH below 7
• Alkaline solutions


  Contain OH− ions, and have a pH above 7
• Neutral solutions


  Have a pH of 7
• Some Tests for Gases


  • hydrogen: apply a lit splint - squeaky pop
  • oxygen: apply a glowing splint - splint relights
  • carbon dioxide: bubble through limewater - limewater turns milky
  • ammonia: smell; damp red litmus paper - pungent smell; red litmus paper turns blue
• Atomic Structure Particles

  • proton: +1 relative charge, 1 relative mass, in nucleus
  • neutron: 0 relative charge, 1 relative mass, in nucleus
  • electron: -1 relative charge, negligible relative mass, orbiting nucleus
• Electron Shell Information

  • Shell 1: maximum 2 electrons
  • Shell 2: maximum 8 electrons
  • Shell 3: maximum 8 electrons
• Group Electron Configuration

  • Group I: 1 outer shell electron
  • Group II: 2 outer shell electrons
  • Group III: 3 outer shell electrons
  • Group IV: 4 outer shell electrons
  • Group V: 5 outer shell electrons
  • Group VI: 6 outer shell electrons
  • Group VII: 7 outer shell electrons
  • Group 0: Full outer shell (8, except He = 2)