Pi bond
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In chemistry, pi bonds (π bonds) are those bonds between two atoms in a molecule that do not exhibit orbital hybridization. Pi bonds are named after the Greek letter "π", as in p orbitals. Pi bonds are direct sharing of electrons between two atoms' p orbitals. Pi bonds are weaker than sigma bonds because their orbitals go further from the positive charge of the nucleus, which requires more energy. As a result, sigma bonds are naturally preferred over pi bonds. However, there is a limit of one sigma bond for each pair of atoms. Atoms with double bonds or triple bonds have one sigma bond and the rest are usually pi bonds. Pi bonds result from parallel orbital overlap: the two combined orbitals meet lengthwise and create longer bonds than the sigma bonds. Electrons in pi bonds are sometimes referred to as pi electrons.