Chemical bonding is the process of bonding together different atoms to form a molecule. For example, oxygen made up of two oxygen atoms bonded together chemically. The chemical bonds hold the atoms together through forces of attraction. For example, oxygen makes O2.
Covalent bonding is when the bonds share their electrons in an attempt to make up the necessary electrons to fill an orbit. For example, Water is made up using covalent bonding. The chemical element for water is H2O, meaning that it contains 2 hydrogen atoms and 1 oxygen atom.
Oxygen has two electrons in its inner orbit and six in its outer orbit. This means that it needs two more electrons to become a noble gas. When it combines with two hydrogen atoms (both containing one electron), oxygen gains two more electrons.
Two electrons can also be shared in the one molecule, this is known as a double bond. Oxygen is an example of a double bond. The chemical element for oxygen is O2 and as discussed one oxygen atom only has six electrons in its outer orbit. This means that one oxygen atom must share two electrons with another oxygen atom in order for them both to have eight electrons in their outer orbit.