<p>This thesis presents briefly the application of quantum mechanics on systems ofchemical interest, i.e., the field of quantum chemistry and computational chemistry.The molecules of the ten-electron series, hydrogen fluoride, water, ammonia,methane and neon, are taken as computational examples. Some applications ofquantum chemistry are then shown on these systems, with emphasis on the natureof the molecular bonds. Conceptual methods of chemistry and theoreticalchemistry for these systems are shown to be valid with some restrictions, as theseinterpretations does not represent physically measurable entities.The orbitals and orbital energies of neon is studied, the binding van der Waalsinteractionresulting in a Ne2 molecule is studied with a theoretical bond lengthof 3.23 °A and dissociation energy of 81.75 μEh. The equilibrium geometries ofFH, H2O, NH3 and CH4 are studied and the strength and character of the bondsinvolved evaluated using bond order, dipole moment, Mulliken population analysisand L¨owdin population analysis. The concept of electronegativity is studied in thecontext of electron transfer. Lastly, the barrier of inversion for NH3 is studied, withan obtained barrier height of 8.46 mEh and relatively constant electron transfer.</p>

This thesis presents briefly the application of quantum mechanics on systems ofchemical interest, i.e., the field of quantum chemistry and computational chemistry.The molecules of the ten-electron series, hydrogen fluoride, water, ammonia,methane and neon, are taken as computational examples. Some applications ofquantum chemistry are then shown on these systems, with emphasis on the natureof the molecular bonds. Conceptual methods of chemistry and theoreticalchemistry for these systems are shown to be valid with some restrictions, as theseinterpretations does not represent physically measurable entities.The orbitals and orbital energies of neon is studied, the binding van der Waalsinteractionresulting in a Ne2 molecule is studied with a theoretical bond lengthof 3.23 °A and dissociation energy of 81.75 μEh. The equilibrium geometries ofFH, H2O, NH3 and CH4 are studied and the strength and character of the bondsinvolved evaluated using bond order, dipole moment, Mulliken population analysisand L¨owdin population analysis. The concept of electronegativity is studied in thecontext of electron transfer. Lastly, the barrier of inversion for NH3 is studied, withan obtained barrier height of 8.46 mEh and relatively constant electron transfer.