1. Ionic Compounds

2. Ionic Compounds
Compounds that contain ions are called Ionic Compounds.
e.g. sodium chloride has the formula NaCl – this means the ratio of sodium ions (Na+), to chloride ions (Cl-) is 1:1
A small crystal of NaCl contains billions of sodium ions and chloride ions in a lattice structure.

4. Ionic Compounds
Every ionic compound contains cations and anions held together by the attraction of their opposite charges.
Ionic compounds form between metals and non-metals.
In solution, they conduct electricity.

5. NaF – single charge ions
Sodium atom
Fluorine Atom F - + Na
Fluoride Ion
Sodium ion

6. MgS – double charge ion Mg S Mg S Magnesium atom Sulfur Atom 2+ 2-
Magnesium Ion
Sulfide Ion

7. Writing Ionic Formulae
Ionic compounds contain cations and anions.
The number of positive charges must be balanced by an equal number of negative charges.

8. Examples
Mg2+
O2-
A magnesium ion has a charge of 2+ and an oxide ion has a charge of 2-. They are equal so the formula for magnesium oxide is MgO, with 1 Magnesium and 1 Oxide.

9. Example
Cl-
Ca2+
Calcium has a charge of 2+ but chloride only has 1-. The charges are not equal. Charges need to be balanced by adding another chloride ion. CaCl2
Cl-
Ca2+
Cl-