Electron atomic and molecular orbitals, showing a Pi-bond at the bottom right of the picture.

In chemistry, pi bonds (π bonds) are covalent chemical bonds where two lobes of one involved electron orbital overlap two lobes of the other involved electron orbital. Only one of the orbital's nodal planes passes through both of the involved nuclei. Image File history File links Electron_orbitals. ... Image File history File links Electron_orbitals. ... Chemistry - the study of atoms, made of nuclei (conglomeration of center particles) and electrons (outer particles), and the structures they form. ... Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or sometimes between atoms and other covalent bonds. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... In chemistry, an atomic orbital is the region in which an electron may be found around a single atom. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ...

Two p-orbitals forming a π-bond.

The Greek letter π in their name refers to p orbitals, since the orbital symmetry of the pi bond is the same as that of the p orbital when seen down the bond axis. P orbitals usually engage in this sort of bonding. However, d orbitals can engage in pi bonding also. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... Electron configuration is the arrangement of electrons in an atom, molecule or other body. ...

Pi bonds are usually weaker than sigma bonds because their (negatively charged) electron density is further from the positive charge of the atomic nucleus, which requires more energy. From the perspective of quantum mechanics, this bond weakness is explained by significantly less overlap between the component p-orbitals due to their parallel orientation. Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ bonds) are a type of covalent chemical bond. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... Fig. ...

Although the pi bond by itself is weaker than a sigma bond, pi bonds are most often found in multiple bonds together with sigma bonds and the combination is stronger than either bond by itself. This can be seen from comparison of the carbon-carbon bond lengths in ethane (154 pm), ethylene (133 pm) and acetylene (120 pm). In molecular geometry, bond length or bond distance is the distance between two bonded atoms in a molecule. ... Ethane is a chemical compound with chemical formula C2H6. ... Picometre (American spelling: picometer) is an SI measure of length that is equal to 10−12 of a metre. ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... Acetylene (systematic name: ethyne) is the simplest alkyne hydrocarbon, consisting of two hydrogen atoms and two carbon atoms connected by a triple bond. ...

Top: two parallel p-orbitals. Bottom: pi bond formed by overlap. Pink and gray represent a ball and stick model of the molecular fragment that contains the pi bond.

Pi bond breaking when bond rotates because parallel orientation is lost. Pink and gray represent a ball and stick model of the molecular fragment that contains the pi bond.

Two s-orbitals continue to overlap when bond rotates because orientation is along axis. Circles represent s orbitals. Ellipses represent merged sigma bond. Pink and gray represent a ball and stick model of the molecular fragment that contains the sigma bond.

Two atoms connected through double bonds or triple bonds usually have one sigma bond between them and one or more pi bonds. Pi bonds result from parallel orbital overlap: the two combined orbitals meet lengthwise and create more diffuse bonds than the sigma bonds. Electrons in pi bonds are sometimes referred to as pi electrons. Molecular fragments joined by a pi bond cannot rotate about that bond unless the pi bond breaks because rotation involves destroying the parallel orientation of the constituent p orbitals. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ...

Special cases

Pi bonds do not necessarily have to connect a pair of atoms that are also sigma-bonded. Sometimes pi bonds occur between atoms and other bonds (as opposed to a pair of atoms), and sometimes there is no sigma bond at all.

In certain metal complexes, pi interactions between a metal atom and the sigma antibond of molecular hydrogen play a critical role in the reduction of some organometallic compounds. Alkyne and alkene pi antibonding orbitals also often pi-bond "side-on" with metal atoms. Antibonding (or anti-bonding) is a type of chemical bonding. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... The structural formula of 2-butyne, a simple alkyne-containing molecule Alkynes are hydrocarbons that have at least one triple bond between two carbon atoms, with the formula CnH2n-2. ... The chemical structure of ethylene, the simplest alkene. ...

In some cases of multiple bonds between two atoms, there is no sigma bond at all, only pi bonds. Examples are diiron hexacarbonyl (Fe₂(CO)₆), dicarbon (C₂) and the borane B₂H₂. In these compounds the central bond consists only of pi bonding, and in order to achieve maximum orbital overlap the bond distances are much shorter than expected.^[1] A borane is an inorganic chemical compound of boron and hydrogen. ...

See also

• Aromatic interaction
• Chemical bond
• Delta bond
• Molecular geometry
• Sigma bond

In supramolecular chemistry, an aromatic interaction (or π-π interaction) is a noncovalent interaction between organic compounds containing aromatic moieties. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ... Delta bonds are bonds which contain two nodal planes, whose intersection is a line containing the segment joining the two bonded species. ... Geometry of the water molecule Molecular geometry or molecular structure is the three dimensional arrangement of the atoms that constitute a molecule, inferred from the spectroscopic studies of the compound. ... Electron atomic and molecular orbitals, showing among others the sigma bond of two s-orbitals and a sigma bond of two p-orbitals In chemistry, sigma bonds (σ bonds) are a type of covalent chemical bond. ...

References

1. ^ Bond length and bond multiplicity: σ-bond prevents short π-bonds Eluvathingal D. Jemmis, Biswarup Pathak, R. Bruce King, Henry F. Schaefer III Chemical Communications, 2006, 2164 - 2166 Abstract