2. Atoms, ions and compounds

• Relative isotopic mass


  The mass of an atom relative to 1/12 of the mass of an atom of carbon-12.
• Isotope

  Atoms of the same element that have the same number of electrons and protons, but a different number of neutrons and different masses.
• Mass to charge ratio

  Relative mass of an ion / relative charge of an ion
• Hydroxide ion

  OH-
• Nitrate ion 


  NO3-
• Nitride ion


  NO2-
• Ammonium ion 


  NH4+
• Ammonia ion


  NH3+
• Hydrocarbonate ion

  HCO3-
• Carbonate ion


  CO32-
• Manganate ion

  MnO4-
• Sulphate

  SO42-
• Sulphite ion

  SO3 2-
• Dichromate ion


  Cr2O2 2-
• Phosphate ion


  PO4 3-
• Relative isotopic mass (Ar) formula


  Ar = (relative isotopic mass x1 % abundance)+ (relative isotopic mass x2 % abundance) / 100