PART_19 WHAT IS VALENCE BOND THEORY?is a theory which describes chemical bonding. VBT states that the overlap of incompletely filled atomic orbitals leads to the formation of a chemical bond between two atoms.Valence Bond theory describes covalent bond formation as well as the electronic structure of molecules.What are the two principles of valence bond theory?According to valence bond theory, a covalent bond results when two conditions are met: (1) an orbital on one atom overlaps an orbital on a second atom and (2) the single electrons in each orbital combine to form an electron pair.bond theory?The two exceptions to the octet rule are boron and aluminum. They do not form ionic compounds usually due to high ionization enthalpy and electron gain enthalpy.Well! Thanks for all!!!