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Encyclopedia > Octet rule
The bonding in carbon dioxide (CO2): all atoms are surrounded by 8 electrons, according to the octet rule. CO2 is thus a stable molecule.
The bonding in carbon dioxide (CO2): all atoms are surrounded by 8 electrons, according to the octet rule. CO2 is thus a stable molecule.

The octet rule is a simple chemical rule of thumb that states that atoms tend to combine in such a way that they each have eight electrons in their valence shells, giving them the same electronic configuration as a noble gas. The rule is applicable to the main-group elements, especially carbon, nitrogen, oxygen, and the halogens, but also to metals such as sodium or magnesium. In simple terms, molecules or ions tend to be most stable when the outermost electron shells of their constituent atoms contain eight electrons. Image File history File links Created with gimp by me, this is a example for the octeto rule http://es. ... Carbon dioxide (chemical formula: ) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... For other uses, see Chemistry (disambiguation). ... A rule of thumb is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. ... Properties For alternative meanings see atom (disambiguation). ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... The valence shell is the outermost shell of an atom, which contains the electrons most likely to account for the nature of any reactions involving the atom and of the bonding interactions it has with other atoms. ... Electron configuration is the arrangement of electrons in an atom, molecule or other body. ... This article is about the chemical series. ... For other uses, see Carbon (disambiguation). ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about the chemical element and its most stable form, or dioxygen. ... The halogens are a chemical series. ... For sodium in the diet, see Salt. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... Example of a sodium electron shell model An electron shell, also known as a main energy level, is a group of atomic orbitals with the same value of the principal quantum number n. ...

Contents

History

In the late 19th century it was known that coordination compounds (formerly called “molecular compounds”) were formed by the combination of atoms or molecules in such a manner that the valencies of the atoms involved apparently became satisfied. In 1893, Alfred Werner showed that the number of atoms or groups associated with a central atom (the “co-ordination number”) is often 4 or 6; other coordination numbers up to a maximum of 8 occur, but less frequently. In 1904 Richard Abegg formulated what is now known as Abegg's rule, which states that the difference between the maximum positive and negative valences of an element is frequently eight. This rule was used later in 1916 when Gilbert N. Lewis formulated the “octet rule” in his cubical atom theory. Alfred Werner (December 12, 1866 - November 15, 1919) was a German Nobel prize-winning chemist. ... Richard Wilhelm Heinrich Abegg (1869 – 1910) was a German chemist and pioneer of valence theory. ... In chemistry, Abegg’s rule states that the difference between the maximum positive and negative valence of an element is frequently eight. ... For other uses, see Valence. ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its nucleus. ... Lewis in the Berkeley Lab Gilbert Newton Lewis (October 23, 1875-March 23, 1946) was a famous American physical chemist. ... The cubical atom was an early atomic model developed by Gilbert N. Lewis in 1916 to account for the phenomenon of valency. ...


Overview

In short, an element's valence shell is full and most stable when it contains eight electrons (this stability is the reason that the noble gases are so unreactive). Note that a "full shell" means that there are the eight electrons in the valence shell when the next shell starts filling, even though higher subshells (d, f, etc.) have not been filled. There can be at most eight valence electrons in a ground-state atom because p subshells are always followed by the s subshell of the next shell. This means that once there are 8 valence electrons (when the p subshell is filled), the next additional electron goes into the next shell, which then becomes the valence shell.


A consequence of the octet rule is that atoms generally react by gaining, losing, or sharing electrons in order to achieve a complete octet of valence electrons. Reaction of atoms occurs primarily in two ways: ionically and covalently. Sodium and chlorine bonding ionically to form sodium chloride. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ...


Some of the atoms for which the octet rule are most useful are:

For other uses, see Carbon (disambiguation). ... This article is about the chemical element and its most stable form, or dioxygen. ... The halogens are a chemical series. ...

Exceptions

  • The duet rule of the first shell - the noble gas helium has two electrons in its outer shell, which is very stable. (Since there is no 1p subshell, 1s is followed immediately by 2s, and thus shell 1 can only have at most 2 valence electrons). Hydrogen only needs one additional electron to attain this stable configuration, while lithium needs to lose one.
  • Electron deficiency occurs in covalent compounds when an atom has fewer than eight electrons, and has no unpaired electrons with which to make more bonds. This is frequently seen in boron compounds, which often only have 6 electrons in the valence shell (e.g. BF3), and also occurs in some reactive species like carbenes.
  • Free radicals (e.g. nitric oxide) contain one or more atoms which have an odd number of electrons.
  • Atoms with 3 or more electron shells can accommodate more than eight electrons in their outer shell (hypervalency). Examples include:
  • The 18-Electron rule overrides the octet rule in transition metals.

General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ... This article is about the chemistry of hydrogen. ... This article is about the chemical element. ... Electron deficiency occurs when a compound has too few valence electrons for the connections between atoms to be described as covalent bonds. ... For other uses, see Boron (disambiguation). ... Boron trifluoride is the chemical compound with the formula BF3. ... In chemistry a carbene is a short-lived and highly reactive organic molecule with a divalent carbon atom with only six valence electrons and the general formula: R1R2C: . The carbon atom is sp2 hybridised with an empty p-orbital extending above and below a plane containing R1 and R2 and... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... A hypervalent molecule is a molecule that contains one or more typical elements (group 1, 2, 13-18) formally bearing more than eight electrons in their valence shells. ... General Name, symbol, number phosphorus, P, 15 Chemical series nonmetals Group, period, block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... Phosphorus pentachloride is the chemical compound with the formula PCl5. ... This article is about the chemical element. ... Sulfur hexafluoride is an inorganic compound with the formula SF6. ... The 18-electron rule is a rule of thumb used primarily in transition metal chemistry for characterizing and predicting the stability of metal complexes. ... In chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings: It commonly refers to any element in the d-block of the periodic table, including zinc, cadmium and mercury. ...

See also

G. N. Lewis Lewis structures, also called electron-dot structures or electron-dot diagrams, are diagrams that show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule [1] [2]. A Lewis structure can be drawn for any covalently-bonded molecule... Electron counting is a formalism used for classifying compounds and for explaining or predicting electronic structure and bonding. ... The 18-electron rule is a rule of thumb used primarily in transition metal chemistry for characterizing and predicting the stability of metal complexes. ...

  Results from FactBites:
 
Vikki Kowalski (3092 words)
Of course, the octet rule isn't universally true, but even many of the exceptions to it can be explained as special cases that conform to most of its implications.
The story of the octet rule begins in the 1850's, when chemistry's basic ideas of what things were made out of resembled today’s: matter was composed of molecules, which were in turn built out of atoms somehow connected together.
The octet rule can be used to examine the periodic table and explain the similarities and differences between various groups of elements.
octet rule: Definition and Much More from Answers.com (491 words)
The octet rule is a simple chemical rule of thumb that states that atoms tend to combine in such a way that they each have eight electrons in their valence shells, similar to the electronic configuration of a noble gas.
The rule is applied to the main-group elements, especially carbon, nitrogen, oxygen, and the halogens.
The octet rule also states that atoms react generally by gaining, losing, or sharing electrons in order to achieve a complete octet of 8 valance electrons.
  More results at FactBites »

 
 

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