The double bond rule states that chemical element

Chemical element

A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

s with a principal quantum number

Principal quantum number

In atomic physics, the principal quantum symbolized as n is the firstof a set of quantum numbers of an atomic orbital. The principal quantum number can only have positive integer values...

greater than 2 (e.g. Period 3 element

Period 3 element

A period 3 element is one of the chemical elements in the third row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical...

s and lower) do not form multiple bonds (e.g. double bond

Double bond

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...

s and triple bond

Triple bond

A triple bond in chemistry is a chemical bond between two chemical elements involving six bonding electrons instead of the usual two in a covalent single bond. The most common triple bond, that between two carbon atoms, can be found in alkynes. Other functional groups containing a triple bond are...

s) with themselves or with other elements. The double bonds if they exist are weak due to weak pi bond

Pi bond

In chemistry, pi bonds are covalent chemical bonds where two lobes of one involved atomic orbital overlap two lobes of the other involved atomic orbital...

s as a results of poor orbital overlap.

This rule was challenged and ultimately made obsolete starting from 1981 with the discovery of silicon and phosphorus double bonds. Double bonds that would ordinarily not form can be stabilized with proper functional groups either electronically or sterically (kinetic stabilization).

Double bonds for carbon and nearest neighbours
	boron Boron Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...	carbon Carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...	nitrogen Nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...	oxygen Oxygen Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...	silicon Silicon Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...	phosphorus Phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...	sulfur Sulfur Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
boron Boron Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...	diborenes	alkylideneboranes	aminoboranylidenes rare	oxoborane Oxoborane In chemistry, an oxoborane is any chemical compound containing a boron atom with a terminal oxygen atom. The compound class is of some relevance to academic research... s rare, rapid oligomerization	not known	boranylidenephosphanes, rare, stable compounds are known	thioxoboranes , rare
carbon Carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...		alkene Alkene In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond... s	imine Imine An imine is a functional group or chemical compound containing a carbon–nitrogen double bond, with the nitrogen attached to a hydrogen atom or an organic group. If this group is not a hydrogen atom, then the compound is known as a Schiff base... s	carbonyl Carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups.... s , oxonium ion Oxonium ion The oxonium ion in chemistry is any oxygen cation with three bonds. The simplest oxonium ion is the hydronium ion H3O+. Another oxonium ion frequently encountered in organic chemistry is obtained by protonation or alkylation of a carbonyl group e.g... s	silenes	phosphaalkene Phosphaalkene Phosphaalkenes are organophosphorus compounds with double bonds between carbon and phosphorus with the formula R2C=PR. In the compound phosphorine one carbon atom in benzene is replaced by phosphorus... s	thioketone Thioketone Thioketones are organosulfur compounds related to conventional ketones. Instead of the formula R2C=O, thioketones have the formula R2C=S. Unhindered alkylthioketones are typically unstable; such compounds tend to form polymers or rings.-Preparative methods:Thiones are usually prepared from ketones... s
nitrogen Nitrogen Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...			Azo compound Azo compound Azo compounds are compounds bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. IUPAC defines azo compounds as: "Derivatives of diazene , HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene." The more... s	nitroso compounds Nitroso Nitroso refers to a functional group in organic chemistry which has the general formula RNO. Nitroso compounds are a class of organic compounds containing the nitroso functional group, R−N=O....	silanimines, rare easy oligomerization, only at low temp.	phosphazene Phosphazene Phosphazenes are a class of chemical compounds in which a phosphorus atom is covalently linked to a nitrogen atom by a double bond and to three other atoms or radicals by single bonds. While other substitutions produce relatively persistent compounds, in organic synthesis the term largely refers to...	sulfilimine Sulfilimine A sulfilimine is a type of chemical compound containing a sulfur to nitrogen double bond. The parent compound is sulfilimine H2S=NH. Examples are methylphenylsulfoximine and S,S-diphenylsulfilimine :-Sulfilimine bonds in proteins:... s
oxygen Oxygen Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...				dioxygen	Silanones Si=O bonds do not form oligomerisation to siloxane Siloxane A siloxane is any chemical compound composed of units of the form R2SiO, where R is a hydrogen atom or a hydrocarbon group. They belong to the wider class of organosilicon compounds.... , only fleeting evidence	Numerous, e.g. phosphine oxide Phosphine oxide Phosphine oxides are either inorganic phosphorus compounds such as phosphoryl trichloride or organophosphorus compounds with the formula OPR3, where R = alkyl or aryl... s , phosphonate Phosphonate Phosphonates or phosphonic acids are organic compounds containing C-PO2 or C-PO2 groups . Bisphosphonates were first synthesized in 1897 by Von Baeyer and Hofmann. An example of such a bisphosphonate is HEDP . Since the work of Schwarzenbach in 1949, phosphonic acids are known as effective... s, Phosphinate Phosphinate Phosphinates are organophosphorus compounds with the formula OPR2.-See also:*Phosphine - PR3*Phosphine oxide - OPR3*Phosphinite - PR2*Phosphonite - P2R*Phosphite - P3*Phosphonate - OP2R*Phosphate - OP3... s, phosphate Phosphate A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in... s	sulfinyls
silicon Silicon Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...					disilene Disilene Disilenes are compounds containing a silicon–silicon double bond and are considered to be heavier analogues of alkenes. They are sometimes also called disilaalkenes.-History:... s	Silylidenephosphanes a.k.a. phosphasilenes rare	silanethiones , rare easy oligomerization
phosphorus Phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...						diphosphene Diphosphene In chemistry, a diphosphene is an organophosphorus compound that has a phosphorus-phosphorus double bond, denoted by R-P=P-R'. These compounds are not common but are of theoretical interest. Normally, compounds with the empirical formula RP exist as rings. However, when the organic substituent is... s	Common, for example in thiophosphate Thiophosphate A thiophosphate is a family of compounds and anions with the general chemical formula PS4-xOx3- . The state of protonation is usually not specified. They could be bound to as many as three protons for the neutral H3PS4-xOx species. Two protons correspond to the related monoanions, and one... s and in phosphine sulfides for example triphenylphosphine sulfide Triphenylphosphine sulfide Triphenylphosphine sulfide is the organophosphorus compound with the formula 3PS, usually written Ph3PS . It is a colourless solid, which is soluble in a variety of organic solvents.... , certain dithiadiphosphetanes
sulfur Sulfur Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...							disulfur Disulfur Disulfur is the diatomic molecule with the formula S2. It is analogous to the dioxygen molecule but rarely occurs at room temperature. This violet gas is commonly generated by heating sulfur above 720 °C and comprises 99% of vapor species at low pressure at 530 °C. S2 is one of minor components... , thiosulfoxide Thiosulfoxide A thiosulfoxide is a chemical compound containing a sulfur to sulfur double bond of the type RR'S=S with R and R' both alkyl or aryl residues. A 1982 review concluded that there was as yet no definitive evidence for the existence of stable thiosulfoxides which can be attributed to the double bond... s