What is the Octet Rule?

The octet ascendancy dictates the atoms are most stable when their valence shells room filled through eight electrons. That is based on the observation that the atoms of the key group facets have a tendency to take part in chemistry bonding in such a means that every atom of the result molecule has actually eight electrons in the valence shell. The octet preeminence is only applicable to the main team elements.

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The molecule of the halogens, oxygen, nitrogen, and also carbon are recognized to obey the octet rule. In general, the elements that follow this preeminence include the s-block elements and the p-block aspects (except hydrogen, helium, and lithium).

The octet dominion can be it was observed in the bonding in between the carbon and also oxygen atom in a carbon dioxide molecule, as portrayed via a Lewis dot framework below.


The common electrons fulfil the valency needs of both the bonded atoms. Thus, it have the right to be detailed that both the oxygen atoms and the carbon atom have actually an octet construction in the CO2 molecule.

Upon observing that the noble gases were chemically inert, the electronic theory of valency was proposed through the German physicist Walther Kossel and also the American chemist Gilbert Lewis. That was based on the propensity of atoms to assume the many stable state possible.


A few examples detailing the chemical bonding of atoms in compliance through the octet ascendancy can be uncovered in this subsection.

NaCl (Sodium Chloride)

This compound attributes an ionic bond between the salt ion (Na+) and also the electronegative chloride ion (Cl–).The chlorine atom hold 7 electrons in the valence shell and also can attain an octet configuration by getting an electron.The outermost covering of sodium has actually one electron. If it loser this electron, the second shell would end up being the valence covering (which is already filled through 8 electrons). Thus, the Na+ ion is more stable than metallic sodium.The sodium cation and the chloride anion now form an ionic bond, and also the resulting molecule attributes octet configurations because that both the participating atoms.

MgO (Magnesium Oxide)

The magnesium atom easily loses two electrons to acquire the stable digital configuration that neon. This leader to the formation of the Mg2+Similarly, oxygen gains 2 electrons to form the O2-The electrostatic attraction the arises in between these two ions leads to the development of an ionic bond in between them.Both the atom in a molecule the MgO have actually stable octet configurations.

Exceptions to the Octet Rule

Not all elements and compounds monitor the octet rule. Some of the exception to this preeminence are listed below.

An ion, atom, or a molecule containing an unpaired valence electron is dubbed a free radical. These species disobey the octet rule. However, they are an extremely unstable and tend come spontaneously dimerize.Since the very first shell have the right to only accommodate two electrons, facets such as lithium, helium, and hydrogen follow the duet rule rather of the octet rule. For example, lithium deserve to lose an electron to have a stable configuration in i m sorry the valence covering holds 2 electrons.Due to the visibility of a d-orbital, the shift elements perform not follow the octet rule. The valence shells of this atoms can hold 18 electrons.

It can be noted that some electron deficient molecules such together boranes and also carboranes follow Wade’s rule in stimulate to obtain stability. This molecules attribute 3c-2e binding (three centred bonds) in which two electrons are shared by three atoms.

The expanded Octet – Hypervalency

Some key group facets have the capability to type hypervalent compounds. Examples include sulfur hexafluoride (SF6) and phosphorus pentachloride (PCl5). If every the phosphorus-chlorine bond in a PCl5 molecule space covalent, it would imply that the phosphorus molecule is violating the octet ascendancy by stop a total of 10 valence electrons.

The development of five bonds by the phosphorus molecules can be described by the sp3d hybridization in PCl5. Here, one ‘s’ orbital, 3 ‘p’ orbitals, and one ‘d’ orbital experience hybridization to type an sp3d hybrid. This hybrid orbital forms five covalent bonds with the five chlorine atoms.


The framework of the hypervalent PCl5 molecule is trigonal bipyramidal, as portrayed above.

Frequently inquiry Questions

How is the Octet preeminence Useful?

The chemistry behaviour the the key group aspects can it is in predicted v the aid of the octet rule. This is due to the fact that the preeminence only entails ‘s’ and ‘p’ electrons, whereby the octet corresponds to an electron configuration ending with s2p6. These elements tend to form bonds in stimulate to attain stable achieve octet configurations.

Do the Oxygen atom in O2 Molecules have Octet Configurations?

Yes, each oxygen atom in the O2 molecule is surrounded by a full of 8 valence electrons. Oxygen has a complete of 6 electrons in the valence shell. In order to attain a secure octet, the 2 oxygen atoms share a total of four electrons via a twin bond.

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List Four facets that execute not obey the Octet Rule

Since ‘1p’ subshells carry out not exist, some aspects find stability in 1s2 configurations. Top top the various other hand, some facets exhibit hypervalency and have the capability to type hypervalent molecules. Some aspects that disobey the octet ascendancy include:


Thus, a short explanation that the octet rule is provided in this article together with its exceptions. To learn more about principles related to chemistry bonding, such together hybridization, register through BYJU’S and download the mobile applications on her smartphone.