Sigma bond

In chemistry, Sigma Bonds are those bonds between atoms in a molecule that exhibit orbital hybridization. Sigma bonds are named after the Greek letter "σ", as in s orbitals. Sigma bonds require that both atoms give an electron from the s orbital in conjunction with additional electrons from the p and sometimes d (and above) orbitals. Sigma bonds are the strongest type of covalent bonds. They result in a head-to-head orbital overlap - the two combined orbitals meet at the more narrow points. Electrons in sigma bonds are sometimes referred to as sigma electrons.