key concepts in chemsitry

• covalent bonds and formula :

  Ammonia = NH

  Carbon dioxide = CO2

  Methane = CH4

  Sulfur dioxide = SO2

  Water = H2O
• ionic compounds :

  Sodium = Na+

  Magnesium = Mg2+

  Chloride = Cl-

  Oxide = O2-
• simple formulae :

  Sodium chloride = NaCl

  Sodium oxide = Na2O

  Magnesium oxide = MgO

  Magnesium chloride = MgCl2
• aqueous solution - forms when a substance dissolves in water
• balancing equations :

  in an equation on both sides the number of atoms should be the same, so you add the numbers