Molekularorbitalsicht

Molekularorbitalsicht is the German term for the molecular orbital (MO) approach to chemical bonding. It is a quantum‑mechanical model that describes electrons in a molecule as occupying orbitals that are spread over the whole molecule rather than localized between specific atomic nuclei. In this view each atom contributes its atomic orbitals, which combine according to symmetry and energy considerations to form bonding, non‑bonding and antibonding molecular orbitals. The occupation of these orbitals by electrons follows the Pauli exclusion principle, Hund's rule and the Aufbau principle.

The molecular orbital approach was first developed in the early twentieth century by chemists such as Friedrich Hund and Linus Pauling, and it has since become a standard part of modern theoretical chemistry. It provides a natural explanation for phenomena that are difficult to account for with the simpler valence‑bond theory, such as resonance in aromatic compounds, magnetic properties of transition metal complexes, and the origin of spectroscopic bands.

A key concept in MO theory is the energy separation between bonding and antibonding orbitals, which determines bond strength and reactivity. The MO scheme also predicts the electronic wave function’s symmetry, allowing the calculation of selection rules for spectroscopic transitions. While the approach gives a global, delocalized picture, it is computationally demanding and often requires approximations such as the linear combination of atomic orbitals (LCAO) or density functional theory (DFT). Nevertheless, the Molekularorbitalsicht remains a cornerstone of contemporary chemistry, providing insight into electronic structure, chemical reactivity, and molecular spectroscopy.