Antibonding (or anti-bonding) is a type of chemical bonding. An antibonding orbital is a form of molecular orbital (MO) that is located outside the region of two distinct nuclei. The overlap of the constituent atomic orbitals is said to be 'out of phase' and as such the electrons present in each antibonding orbital are repulsive and act to destabilize the molecule as a whole. A chemical bond is the physical phenomenon of chemical substances being held together by attraction of atoms to each other through sharing, as well as exchanging, of electrons -or electrostatic forces. ... Electron atomic and molecular orbitals In quantum chemistry, the molecular electronic states, i. ... A stylized Bohr model-like representation of a lithium atom. ... An atomic orbital is the description of the behavior of an electron in an atom according to quantum mechanics. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... The valence shell electron pair repulsion theory or VSEPR is a model in chemistry that aims to generally represent the shapes of individual molecules. ... Reactivity refers to the rate at which a chemical substance tends to undergo a chemical reaction in time. ... In general, a molecule is the smallest particle of a pure chemical substance that still retains its composition and chemical properties. ...

Antibonding molecular orbits (MOs) are normally higher in energy than bonding MOs. They are occupied by two electrons at a time and (in the case of helium), each hydrogen atom can contribute only one electron, therefore only the s (bonding) MO is occupied and the H₂ molecule is more stable than two separate H atoms. General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Properties In chemistry and physics, an atom (Greek άτομον meaning indivisible) is the smallest possible particle of a chemical element that retains its chemical properties. ...

A molecular orbital becomes antibonding as there is actually less electron density between the two nuclei than there would be if there was no bonding interaction at all. When an MO changes sign (from positive to negative) between two atoms, it is said to be antibonding with respect to those atoms. Antibonding orbitals are often labelled with an asterisk (*) on molecular orbital diagrams. Electron density is the measure of the probability of an electron being present at a specific location. ... a asterisk in eurostyle font An asterisk (*) is a typographical symbol or glyph. ...

In molecules with several atoms, such as benzene, a particular MO may be bonding with respect to some adjacent pairs of atoms and antibonding with respect to other pairs. If the bonding interactions outnumber the antibonding interactions, the MO is said to be "bonding," while if the antibonding interactions outnumber the bonding interactions, the MO is said to be "antibonding". Since each carbon atom contributes only one electron to the π-system of benzene, there are six π-electrons and therefore only the three lowest-energy MOs (the bonding ones) are filled. Benzene, also known as C6H6, PhH, and benzol, is an organic chemical compound that is a colorless and flammable liquid with a pleasant, sweet smell. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture In chemistry, pi bonds (Ï€ bonds) are bonds with a single nodal plane containing the line segment between the two atoms. ...

Another particular feature of antibonding is that the antibonding orbital is more antibonding than the bonding orbital is bonding. This leads to the conclusion that the energy of both MOs are raised by the presence of nucleus-nucleus repulsion.

Antibonding orbitals are also important for explaining chemical reactions in terms of molecular orbital theory. Roald Hoffmann and Kenichi Fukui shared the 1981 Nobel Prize in Chemistry for their work and further development of qualitative MO explanations for chemical reactions. A chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved in a chemical reaction are called reactants. ... Roald Hoffmann (born July 18, 1937) is a Polish theoretical chemist. ... Kenichi Fukui (福井謙一 Fukui Kenichi, October 4, 1918 – January 9, 1998) was a Japanese chemist. ... 1981 (MCMLXXXI) was a common year starting on Thursday of the Gregorian calendar. ... List of Nobel Prize laureates in Chemistry from 1901 to the present day. ... Qualitative is an important qualifier in the following subject titles: Qualitative identity Qualitative marketing research Qualitative method Qualitative research THE BIG J This is a disambiguation page — a list of pages that otherwise might share the same title. ...

References

• Atkins, P.W. (2002). Atkins Physical Chemistry. 7th ed. Oxford. ISBN 0198792859
• Orchin, M. Jaffe, H.H. (1967) The Importance of Antibonding Orbitals. Houghton Mifflin. ISBN B0006BPT5O
• The 1981 Nobel Prize in Chemistry