Sigma bonds are formed by the head to head overlap of orbitals, it is denoted by c (sigma). Sigma anti bonding orbitals is denoted by σ. Electron pair in the sigma orbitals are called sigma orbital electrons and the loop formed is called “Sigma Bond”.
Characteristics of Sigma Bond
i. Sigma bonds are formed due to s—- s, s —- p and p—- p overlap between the two atomic orbitals.
ii. Electron density of sigma orbitals is maximum between the two nuclei of bonding atoms.
iii Sigma orbitals are symmetrical w. r. t the line joining the nuclei.
iv. Due to greater extent of overlapping sigma bonds are stronger bonds.
v. The two s – s orbitals can not overlap, so effectively Clue to spherical charge distribution, therefore, s ~ s bond is weak as compared to p – p bond which overlaps very effectively due to their long lobes. The strength of bonds shown as below: