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Identifying Ionic Compounds

Chemistry: Edexcel IGCSE, topic 6.1.7

Identifying Ionic Compounds

An ionic compound formula has no overall charge.

Naming compounds

Naming compounds

  • Ionic compounds made from 2 different elements end in -ide.
  • Ionic compounds made from 3 or more different elements end in -ate.
Compound formulae

Compound formulae

  • Potassium forms K+ and oxygen forms O2-.
  • We need 2 potassium ions (K+) to cancel out the 2- charge to the oxygen. Therefore, the formula becomes K2O.
Brackets

Brackets

  • When there are multiple groups of atoms, we must use brackets.
  • Calcium forms a Ca2+ ion, and a nitrate ion that has the formula NO3-.
  • We need two nitrate ions to cancel out the 2+ charge to the calcium.
  • Therefore, calcium nitrate has a formula Ca(NO3)2.

Test yourself on Identifying Ionic Compounds

  • What is the overall charge of an ionic compound formula?

  • Calcium nitrate has the formula Ca(NO3)2. Calcium forms a Ca2+ ion. What is the charge on a nitrate ion?

  • An ionic compound ending in -ide must have how many different elements?

  • An ionic compound ending in -ate must have how many different elements?

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