You know that all substances are built up of particles, and the simple particles are atoms or ions.
These particles - normally - do not stay alone, but mostly are connected to other particles.
This connecting can happen in different ways, but, always they stick toghether at their outer sides, or: the connection, the bonding always has to do with the outer shell, with the valency electrons.
Only atoms of noble gases remain 'bachelors'. Die do not connect with others.
Every way to connect particles is called a chemical bonding. Of them we discuss three kinds in this chapter.
The result of such a chemical bonding may have big consequences for the properties of the new compound.