Chemistry – Atoms, elements and compounds - Ions and ionic bonds | e-Consult

The high melting and boiling points of ionic compounds are a direct consequence of the strong electrostatic forces of attraction between the oppositely charged ions in the ionic lattice. These forces are non-directional and extend throughout the entire crystal structure, requiring a significant amount of energy to overcome. This energy input is manifested as a high melting point.

In the solid state, the ions are fixed in a regular lattice arrangement. They cannot move freely and therefore cannot carry an electric current. This explains why solid ionic compounds are poor conductors of electricity.

When an ionic compound is melted or dissolved in water, the ions are free to move. In a molten state, the ions are not held in a fixed lattice and can move randomly. In an aqueous solution, the ions are surrounded by water molecules, which also allows them to move freely. This mobility of ions enables them to carry an electric current, making molten and aqueous ionic compounds good conductors of electricity. The forces holding the ions together (electrostatic attraction) are overcome by the energy input (heat or solvation), allowing for ion mobility and electrical conductivity.