Properties of Ionic Compounds

Ionic compounds are substances made up of ions, which are charged particles. These ions are held together by the electrostatic forces of attraction in a process known as ionic bonding. This type of bonding occurs between oppositely charged ions, which are attracted to each other.

Ionic bonding forms a giant lattice structure, in which ions are arranged in a regular, repeating pattern. Positive and negative ions are next to each other, which creates a balance of electric charges within the lattice.

An example of an ionic compound is sodium chloride, which is commonly known as table salt. In the diagram below, you can see the arrangement of ions in solid sodium chloride.

Ionic substances have high melting and boiling points because they are held together by strong ionic bonds. And breaking these ionic bonds requires a lot of energy.

The strength of ionic bonds depends on the charge of the ions. Ions with a higher charge will have stronger electrostatic forces between the charged particles. This means that more energy will be required to break the bonds and separate the ions. Therefore, ionic compounds with ions of higher charges tend to be more stable.

This also means that compounds containing ions with a higher charge will have higher melting and boiling points. You can see this in the table below.

Ionic compoundIons in the compoundMelting pointBoiling point
NaClNa⁺ and Cl⁻801 °C1,413°C
CaCl2Ca²⁺ and Cl⁻772 °C1,935°C

Electrical Conductivity

Ionic compounds are known to be great conductors of electricity when they are in a molten state or dissolved in water. This is because the ions in these substances are free to move and carry charge. Therefore, electricity can flow through the solution.

However, ionic compounds do not conduct electricity as solids because the ions in a solid state are fixed and unable to move. This means that they are unable to carry charge.

At room temperature, ionic compounds are typically in a solid state. However, they often dissolve in water to form an aqueous solution. For example, sodium chloride (table salt) dissolves in water, to form individual sodium ions (Na⁺) and chloride ions (Cl⁻). These ions are free to move and carry charge, making the solution a good conductor of electricity.

Salt (sodium chloride) is poured from a spoon into a flask of water, where it dissolves to release its ions.