Key Concepts: Ionic Compounds

Ionic compounds are formed when a metal reacts with a non-metal. They consist of positive cations and negative anions.
The metal atoms lose electrons to form positive ions, while the non-metal atoms gain these electrons to form negative ions.
These ions have different charges, but the total positive charge of the cations equals the total negative charge of the anions.
The particles in an ionic compound are held together by a strong force of attraction known as ionic bonding.
Ionic compounds have high melting and boiling points due to the strong forces of attractions between the ions.
In solid state, ionic compounds don’t conduct electricity since the ions are not free to move. When dissolved or in a molten state, they can conduct electricity because the ions are free to move.
Ionic solids form crystal lattices, which are an ordered, repeating pattern of ions.
Sodium chloride (NaCl) and magnesium oxide (MgO) are common examples of ionic compounds.
The properties of ionic compounds such as solubility, hardness, melting point and boiling point are linked to the size and charge of the ions, and the structure of the compound.
The chemical formula of an ionic compound represents the simplest ratio of ions that provides an electrically neutral compound.
The structure of an ionic compound can be represented in different ways, including as a dot-and-cross diagram or a ball-and-stick model.
The size and charge of ions affect the strength of the ionic bonding, and thus the physical properties of the compound. For example, greater charge and smaller ion size result in stronger ionic bonds.