Table 1.

The physical energy types associated with IQA and its chemical interpretation

Energy type	Physical Foundation	Physicochemical	Chemical concepts
1	Kinetic energy, intra-atomic electron-electron and electron–nucleus potential energy	Steric energy	Steric hindrance
2	Interatomic Coulomb	Electrostatics	Polarity, ionicity
3	Interatomic exchange energy	Bonding Pauli repulsion	Bond order, (hyper)conjugation
4	Interatomic electron correlation energy	Part of van der Waals interaction	dispersion