Electronic Structure
In chemistry, electronic structure is the study of the electronic structure of molecules and the effects of this structure on the properties of molecules. The electronic structure of molecules is a function of their spatial geometry, their symmetry, and the physics of the electrons involved. Electron configuration is the quantum mechanical description of the arrangement of valence electrons in an atom. The configuration of electrons in a neutral atom is described by the quantum numbers, such as the principal quantum number "n", the azimuthal quantum number "l", and the magnetic quantum number "m". Each of these quantum numbers can take on a range of integer values that can be represented by the Slater determinants, or more often by the Pauli matrix. This is similar to the configuration of an electron in a molecule, which is described by the nuclear spin quantum number, the principal quantum number, and the magnetic quantum number. The electron configurations of atoms and molecules obey the same rules. For example, a neutral atom with one valence electron has an electron configuration of 1s22s22p4, while a neutral molecule with one valence electron has an electron configuration of 1s22s22p2. In both cases the configuration is a product of three quantum numbers, which are related by the rules of orbital hybridization. The orbital hybridization of an atom or molecule arises from the interaction between the discrete energy levels of an atom or molecule (i.e. the atomic or molecular orbitals) and the discrete energy levels of each other atom or molecule in a molecule or crystal. It is a consequence of the Pauli exclusion principle, which states that no two electrons in an atom can have the same set of five quantum numbers. This principle dictates that the electrons in a neutral atom occupy discrete energy levels, and three of these can occupy energy levels in the same orbital. The energy levels of the electrons are also often described by the quantum numbers, such as the principal quantum number, the azimuthal quantum number, and the magnetic quantum number. Because of the "allowed" energy levels of the electrons in the atom, the number of electrons that can occupy each energy level is limited. Therefore, the electrons in a neutral atom must occupy orbitals of the same energy. The quantum numbers that describe the energy levels of the electrons in an atom are related by the Pauli exclusion principle, which dictates that no two electrons can have the same set of five quantum numbers. The electrons in a molecule or crystal also obey the Pauli exclusion principle, which dictates that all the electrons must have different values of the five quantum numbers.
