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Octet Rule

Reviewed by Raghvendra GopalCheckmark
Last updated: September 19, 2022

What Does Octet Rule Mean?

The octet rule states that atoms gain or lose electrons to attain an outer shell electron configuration nearest that of a noble gas. The attractive force between atoms is informally measured with this rule.

The octet rule dictates particular electron placement on the orbitals of the atom's nucleus. It also determines whether electrons are added or lost through chemical reactions, and measures chemical reactivity of atoms based upon their specific electron configuration.

The octet rule refers to the phenomenon whereby elements will usually form bonds so as to attain eight electrons in their valence shell in order to become noble gases. The outer shells contain electrons that occupy all available spaces. The bonding patterns and reactivity of such elements can easily be predicted by applying this rule.

Due to the stability of their configuration that is its being full octet with no charge, such gases have no reason to react. They are used because of these advantages they provide in environments where corrosion or damage from electrical discharges is known to occur if the environments were to be filled with air.

Atoms of metals sometimes lose all of their valence electrons, leaving them with an octet that is from the next principal energy level that is lower than its previous state. Atoms of most nonmetals tend to gain electrons to fill their outermost energy level with an octet.


Corrosionpedia Explains Octet Rule

The octet rule describes how elements generally prefer to form bonds so that they can attain eight electrons in their valence shell to become noble gases. Noble gases have outer shells with electrons occupying all available spaces. Bonding behavior and reactivity of elements can be predicted by applying this rule. All elements other than noble gases have a deficiency or surplus of electrons in their valence shell, causing a positive or negative charge. Atoms of elements tend to react in such a way so that it achieves the electronic configuration of noble gases.

Noble metals are generally seen as a metallic chemical element that are resistant to corrosion because of its makeup and is found in nature in its raw form. Noble metals are metals that resist oxidation and corrosion that occur in moist air.

These noble metals are also not easily attacked by acids. Based on its characteristics, they are the opposite of the base metals, which tend to readily oxidize and corrode. Noble metals are more stable while active metals react more with their environment which makes them more likely to corrode. Metals that are considered part of the group of precious metals can be considered noble metals because they are more resistant to interactions with other chemicals which makes them more corrosion-resistant.

Noble metals make great choices for coating and can serve as good protective coating in the form of a metallic layer applied to a metal substrate for corrosion prevention measures.

While this rule generally applies for metals and nonmetals, it is not of much use in dealing with compounds of the transition elements in which d or f orbitals are involved in bonding. Plus, this rule doesn't accurately predict the electron configurations of all molecules and compounds. Consequently, this rule has to be used with care in predicting the electron configurations.

Atoms that accommodate the octet rule have greater stability and emit less energy.

Octet Rule Example

The formula for table salt is NaCl. This is due to Na+ ions and Cl- ions bonding together. If sodium metal and chlorine gas mix under the right conditions, they will form salt. The sodium loses an electron, and the chlorine gains that electron. In the process, a large amount of light and heat is released. The resulting salt is not reactive — it is stable. It will not undergo any explosive reactions, which can happen either for Sodium or chlorine .


Referring to the octet rule, atoms try to get a noble gas electron configuration. Sodium has one valence electron, so when it gives it up, it would result in the same electron configuration as neon. Chlorine has seven valence electrons, so by taking one it will have eight (an octet). Chlorine has the electron configuration of argon due to gaining of electron.

The octet rule would have answered if chlorine gave up all seven of its valence electrons and sodium took them. In that case, both would have the electron configurations of noble gasses, where shell has full. valency. However, their charges would be much higher. It would be Na7- and Cl7+ This is much less stable than Na+ and Cl-. Atoms are generally more stable when they have no charge, or only a small charge.


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