What is Double bond?
[[File:Skeletal-formulae-internal-double-bond.svg|thumb|A diagram of the hydrocarbon hex-3-ene, containing a carbon-carbon double bond. Highlighted in red, the way to draw a double bond in ''skeletal formula. '']] A '''double bond''' in [[chemistry]] is when two [[chemical element]]s are joined together in a [[chemical bond]] and share four bonding [[electron]]s instead of the usual two. The most common double bond is between two [[carbon]] [[atom]]s, and can be found in [[alkene]]s. There are many types of double bonds, such as in a [[carbonyl]] group with a carbon atom and an [[oxygen]] atom. Other common double bonds are found in [[azo compound]]s (N=N), [[imines]] (C=N) and [[sulfoxides]] (S=O). In [[skeletal formula]] the double bond is shown as two [[parallel]] lines (=) between the two joined atoms. When this formula is printed, the [[equals sign]] is used.<ref>{{JerryMarch}}</ref> [[File:Double bond.JPG|thumb|A simplified diagram, showing where the sigma bond and the pi bond exist between two double bonded carbon atoms.]] Double bonds are stronger than [[covalent bond|single bonds]] and double bonds are also shorter. The [[bond order]] is two. Double bonds are also electron-rich, which makes them more [[Reactivity (chemistry)|reactive]]. The two pairs of electrons involved in the bond do not behave in exactly the same way. One pair of electrons forms a stronger ''[[sigma bond|sigma]]''[[sigma bond| bond]], noted by σ and drawn as a straight line between the nuclei of the bonding atoms. While the other pair form a [[pi bond]], π, drawn as two cloud-like areas where the electrons exist, as ''orbitals''.<ref>{{cite web|url=http://www.chemguide.co.uk/atoms/bonding/doublebonds.html|title=covalent bonding - double bonds|website=www.chemguide.co.uk}}</ref><ref>{{Cite web |url=http://chemwiki.ucdavis.edu/Theoretical_Chemistry/Chemical_Bonding/Pictorial_Molecular_Orbital_Theory |title=Pictorial Molecular Orbital Theory - Chemwiki |access-date=2015-04-21 |archive-date=2015-04-21 |archive-url=https://web.archive.o