Electron atomic and molecular orbitals

The Aufbau principle from German "Aufbau" meaning "buildup" (also Aufbau rule or building-up principle), is used to determine the electron configuration of an atom, molecule or ion. The principle postulates a hypothetical process in which an atom is "built up" by progressively adding electrons. As they are added, they assume their most stable conditions (electron orbitals) with respect to the nucleus and those electrons already there. Image File history File links Electron_orbitals. ... Image File history File links Electron_orbitals. ... Electron atomic and molecular orbitals In atomic physics and quantum chemistry, the electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure (eg, a crystal). ... Properties In chemistry and physics, an atom (Greek ἄτομος or átomos meaning indivisible) is the smallest particle still characterizing a chemical element. ... In science, a molecule is a group of atoms in a definite arrangement held together by chemical bonds. ... An electrostatic potential map of the nitrate ion (NO3−). Areas coloured red are lower in energy than areas colored yellow An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged. ... Electron atomic and molecular orbitals In atomic physics, an electron orbital (or simply orbital) is the description of the behavior of an electron in an atom or molecule according to quantum mechanics. ...

According to the principle, electrons fill orbitals starting at the lowest available (possible) energy states before filling higher states (e.g. 1s before 2s). Orbitals are generally filled according to the n+l rule where orbitals with a lower n+l value are filled before those with higher n+l values. In case of equal n+l values, the orbital with a lower n value is filled first. e- redirects here. ... An energy level is a quantified stable energy, which a physical system can have; the term is most commonly used in reference to the electron configuration of electrons, in atoms or molecules. ...

The number of electrons that can occupy each orbital is limited by the Pauli exclusion principle. If multiple orbitals of the same energy are available, Hund's rule says that unoccupied orbitals will be filled before occupied orbitals are reused (by electrons having different spins). The Pauli exclusion principle is a quantum mechanical principle formulated by Wolfgang Pauli in 1925. ... Degenerate orbitals for electrons in an atomic subshell are orbitals at identical energy levels (by definition). ... Hunds rule is a principle of physical chemistry which states that before any two electrons occupy an orbital in a subshell, other orbitals in the same subshell must first each contain one electron. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ...

A version of the Aufbau principle can also be used to predict the configuration of protons and neutrons in an atomic nucleus. In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... This article or section does not adequately cite its references or sources. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...

A common exception to the Aufbau principle is copper. General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Standard atomic weight 63. ...

History

Orbits with low angular momentum (s- and p-orbitals) get closer to the nucleus

The principle takes its name from the German Aufbauprinzip, "building-up principle", rather than being named for a scientist. In fact, it was formulated by the Danish physicist Niels Bohr circa 1920. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Niels (Henrik David) Bohr (October 7, 1885 – November 18, 1962) was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in 1922. ... 1920 (MCMXX) was a leap year starting on Thursday. ...

It was an early application of quantum mechanics to the properties of electrons, and explained chemical properties in physical terms. Each added electron is subject to the electric field created by the positive charge of atomic nucleus and the negative charge of other electrons that are bound to the nucleus. Although in hydrogen there is no energy difference between orbitals with the same principal quantum number n, this is not true for the outer electrons of other atoms. Semiclassically, orbitals with the highest angular momentum are 'circular orbits' outside the inner electrons, but orbits with low angular momentum (s- and p-orbitals) have high orbital eccentricity, get closer to the nucleus and feel on average a less strongly screened nuclear charge. That explains why 4s-orbitals are filled before even 3d-orbitals. Fig. ... e- redirects here. ... This article needs additional references or sources for verification. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... (This page refers to eccitricity in astrodynamics. ...

See also

• electron configuration
• Valence electrons
• Image: Understanding order of shell filling