When atoms join together, we describe this as bonding . When atoms of different elements bond together, the substance that forms is called a compound . The individual particles in the compound are called molecules . Positive ions are called cations . Positive and negative ions attract one another and join together to form a stable structure called a continuous lattice .
Ionic compounds are usually crystalline solids with a high melting point.
They are usually soluble in water but not other solvents. A covalent bond is formed when electrons are shared between atoms, rather than being transferred from one to the other. A covalent bond is a pair of electrons that is shared between two different atoms. Each atom contributes one of the electrons. Both electrons whizz around the electron shells of both atoms, completing both of them.