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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. Sigma bonding is most clearly defined for diatomic molecules using the language and tools of symmetry groups. In this formal approach, a σ-bond is symmetrical with respect to rotation about the bond axis. By this definition, common forms of sigma bonds are s+s, p_z+p_z, and s+p_z, and d_z2+d_z2 (where z is defined as the bond axis). Quantum theory also indicates that molecular orbitals of identical symmetry mix. As a practical consequence of mixing in diatomic molecules, the wavefunctions s+s and p_z+p_z molecular orbitals become blended. The extent of mixing (or blending) depends on the relative energies of the like-symmetry MO's. Image File history File links Image-request. ... Image File history File links Electron_orbitals. ... Image File history File links Electron_orbitals. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... 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. ... The symmetry group of an object (e. ... This article discusses the concept of a wavefunction as it relates to quantum mechanics. ... In chemistry, a molecular orbital is a region in which an electron may be found in a molecule. ...

For homodiatomics, bonding σ orbitals have no nodal planes between the bonded atoms. The corresponding antibonding, or σ* orbital, is defined by the presence of a nodal plane between these two bonded atoms.

Sigma bonds are the strongest type of covalent bonds. Electrons in sigma bonds are sometimes referred to as sigma electrons. Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. ... e- redirects here. ...

The symbol σ is the Greek letter for s. When viewed down the bond axis, a σ MO resembles an s atomic orbital.

Sigma bonds in polyatomic compounds

The concept of sigma bonding is extended, albeit loosely, to describe bonding interactions involving overlap a single lobe of one orbital with a single lobe of another. For example, propane is described as consisting of ten sigma bonds, one each for the two C-C bonds and one each for the eight C-H bonds. The σ bonding in such a polyatomic molecule is highly delocalized, which conflicts with the two-orbital, one-bond concept. Despite this complication, the concept of σ bonding is extremely powerful and hence pervasive. In chemistry, an atomic orbital is the region in which an electron may be found around a single atom. ... Propane is a three-carbon alkane, normally a gas, but compressible to a liquid that is transportable. ...

Sigma bonds in multiply bonded species

Compounds that feature multiple bonds, such as ethylene and chromium(II) acetate have sigma bonds between the multiply bonded atoms. These sigma bonds are supplemented by π-bonds, e.g. in the case of ethylene, and even δ-bonds, e.g. in the case of chromium(II) acetate. Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ... One of the chromium salts of acetic acid is chromium(II) acetate with chemical formula Cr2(CH3COO)4. ...

See also

• Pi bond
• Delta bond
• Molecular geometry