elektronstruktur

Electronic structure describes how electrons are arranged around nuclei in atoms and molecules and the energies associated with those arrangements. In atoms, electrons fill atomic orbitals—regions in space described by quantum numbers that solve the Schrödinger equation. In molecules, electrons occupy molecular orbitals formed from linear combinations of atomic orbitals.

Key principles: Electrons obey the Pauli exclusion principle; the Aufbau principle, and Hund's rule govern how electrons populate orbitals, determining the ground-state electron configuration and spin state.

In atoms, configurations lead to term symbols and energies; spin-orbit coupling and relativistic effects are more pronounced for heavy elements, producing fine structure.

In molecules, bonding and anti-bonding orbitals arise from interactions of atomic orbitals; the energy gap between occupied and unoccupied orbitals (HOMO-LUMO gap) correlates with reactivity and color; excited states access via spectroscopy.

To study electronic structure, theory uses ab initio methods (Hartree-Fock, post-Hartree-Fock methods such as MP2 and CC) and density functional theory (DFT). For excited states, time-dependent DFT (TD-DFT) and multireference methods are used. Experimental techniques include photoelectron spectroscopy, UV-Vis spectroscopy, and X-ray absorption.

The concept underpins chemistry, material science, spectroscopy, and catalysis, providing a framework to predict properties and behavior of atoms and molecules.