chemical formulae

• • If a compound contains only 2 elements it will end in -ide for example Sodium chloride. (sodium and chlorine).
• • If a compound contains 3 elements and the 3rd is oxygen it will end in -ate for example Sodium carbonate.
• Valency of an element is how many bonds it can form.

  The valency depends on the group an element is in:

  • Group 1 = 1
  • Group 2 = 2
  • Group 3 = 3
  • Group 4 = 4
  • Group 5 = 3
  • Group 6 = 2
  • Group 7 = 1
  • Group 8/0 = 0
• Transition metals can change their valency so it is indicated by Roman numerals
• There is one the exception to the 'ide' rule: hydroxide. This contains hydrogen and oxygen
• The valency of a group ion is the same as the value of its charge.