The octet rule is the rule that describes the atoms of the main group elements tends to combine for balance shell with such approach that each atom has eight valence electrons. They tend to have the same electronic configuration as a noble gas. Example of these elements are carbon (C), Nitrogen (N), Oxygen (O), and the halogens and also the metals such as sodium (Na) or magnesium (Mg).
It is the rule of nature that all the things in this universe tend to get balanced. Similarly, few gases known as Nobles Gases have balanced valence shells. And all other elements try to get balanced valence shells.
In this article, we will describe the octet rule and its background along with examples, so read the article until the end.
In 1916, an American physical chemist, Gilbert N. Lewis, created his cubical atom model and the rule of eight. His theory describes that the atoms tend to combine to get the stable state and that is achieved by 8 valence electrons.
The Octet Rule
According to this rule, an atom is considered to be in the stable state if it possess eight electrons in its valence shells, and due to these eight electrons, it is known as octet rule.
This stability is achieved either by sharing own electron or other element’s electron. An atom continues sharing until it gets eight electrons or in other words if the octet is formed. Valence shell is known as the outer shell of an atom and if any atom is successful in achieving the 8 electrons then we say that the atom is stable and the atom has the same configuration of electrons as a Noble Gas.
In the periodic table, the zero group containing the elements helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) are known as noble gases. These are called as noble because they are rarely found on the earth and there outer most shell forms octet and they are the most stable therefore they were believed not to react with any other element.
Other than these, all the elements are not stable. So if they have more electrons they lose them by sharing with those elements that have fewer electrons. And if an element has less electron it will try to gain the electron by sharing to get stable. Briefly, we can say that all the elements share their electrons until the octet is formed in the valence shell as that of noble gases.
Sodium And Chlorine
Chlorine atom possess 7 valence electrons and if it has to fulfill the octet rule then it requires one more electron. Whereas, sodium atom has only 1 electron in its valence shell and it requires 7 electrons to fulfill octet rule.
If they are combined the chlorine atom removes the one valence electron from sodium and completes its 8 electrons. Now it has the configuration similar to Argon noble gas. Now there is no electron left in the valence shell of sodium atom and at this stage, its configuration is similar to neon noble gas
Carbon dioxide is generated through the bonding of 1 carbon atom and 2 oxygen atoms i.e. CO2. Carbon has four electrons in its shell and to fulfill the octet rule it requires four more electrons. Whereas oxygen has six valence electrons and to fulfill the octet rule it would need 2 more electrons.
When carbon and oxygen atoms are combined then Carbon shares its 2 valence electrons with 1 oxygen atom and the other two valence electrons with the second oxygen. Oxygen then, in turn, shares two of its electrons with the carbon atom. This type of sharing is known as covalent bonding because in this no atom losses its electron and all the atoms allow each other to share their electrons to react the octet.
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