One of the theories used to explain molecular bonding is Molecular Orbital Theory. This theory deals with the generation of bonding and antibonding molecular orbitals populated by the electrons in the valence shells of the two bonding atoms.
Part of this theory is the concept of bond order which gauges whether a molecular bond would be stable or unstable.
Bonding: Bonding is a term to describe when atoms donate or share electrons. The electrons that participate in bonding are called valence electrons.
Atoms: Atoms are the smallest units of matter that still maintain the properties of an element. Atoms are made of a nucleus of protons and neutrons and are surrounded by a cloud of electrons.
Electrons: Electrons are negatively charged, subatomic particles that make up atoms. Electrons are donated or shared during molecular bonding.