What is the difference between Octet Rule and Duplet Rule

Octet Rule and Duplet Rule :

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In nature, there exist both chemically active and inert atoms or molecules. This property primarily depends on the number of electrons found in the atoms’ outermost shells. Atoms with unstable electron configurations may become active in order to achieve stability. Since inactive atoms have a full electron configuration, they do not interact with other atoms unless certain circumstances exist. In nature, noble gases are always dormant. They are hence referred to as inert gases. The eighth column of the periodic table is devoted to inert gases.

Noble gases or Inert gases
Noble gases or Inert gases

The electron configuration of the inert gas, which is the most stable form in nature, tends to be obtained by other elements in the same period (row) at the conclusion of that period.

According to the duplet or octet rules, active atoms often fulfil their required number of electrons. The main distinction between an octet and a duplet is that an octet atom or ion has a maximum of eight electrons in its outermost shell, whereas a duplet atom has a maximum of two.

What is a duplet?

An atom with 2 electrons in its outermost shell is called a duplet.

What is a duplet
Helium,a duplet

The smallest elements found in nature are the hydrogen and helium atoms, which have just one orbital around their nucleus. The name of this orbital is 1s orbital. There can be a maximum of two electrons in this orbital.

Helium possesses two electrons, while the hydrogen atom only has one. Thus, helium is referred to as a duplet. Helium is a stable element in nature because it has as many electrons as it can possibly have. As a result, helium is an inert gas as well. However, hydrogen only has one electron, and the orbital that it does have is imperfect. Due to its high reactivity, the hydrogen atom seeks to form covalent bonds with other hydrogen atoms by sharing the two electrons that each possesses.

Once these hydrogen atoms have two electrons in their outermost orbitals, they are known as duplets. However, by removing the electron from its outermost orbital, lithium can also behave like a duplet. Lithium has an electron configuration of 1s2 2s1. It can change into a duplet by taking out the 2s1 electron. In that circumstance, stable duplets of He, H-, and Li+ are possible.

The electron configuration at the end of each duplet is as follows.


Duplet Rule

The tendency of an atom to acquire 2 electrons in the outermost shell.

Atoms with a low atomic number such as hydrogen and helium followed the duplet rule.

What is Octet?

An atom with 8 electrons in its outermost shell is called an octet.

Octet Rule

The tendency of an atom to acquire 8 electrons in the outermost shell in order to attain the noble gas configuration and becomes stable.

Atoms having 7 or less than 7 electrons in their valence shell followed the octet rule.

With the exception of helium, all noble gases are inert and have eight electrons. A noble gas’s final electron configuration is always as follows.

ns2 np6

Neon, for instance, has an electron configuration of 1s2 2s2 2p6. The gas neon is inert.

Some additional elements with one, two, or more electrons tend to lose electrons and acquire the electron configuration of the closest inert gas, whilst other elements with seven, six, or more electrons in the outermost orbital tend to obey the octet rule by gaining electrons from outside. However, some middle-range elements on the periodic table will make new connections with elements that have extra electrons, allowing them to share electrons and create an octet.

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Octet vs Duplet

Topics covered in a video :

  1. What are a duplet and an octet?

2. Difference between octet rule and duplet rule.

3. Which of the following atoms follow the duplet and octet rule?

4. Why is it important for an atom to attain a noble gas configuration.


Octet vs. Duplet

Every element has a tendency to stabilise. Atoms, however, cannot be stable when their electron configurations are incomplete; as a result, they become extremely reactive in an effort to obtain, lose, or share electrons in order to complete their electron shells. Stable atoms or molecules are those that adhere to the octet or duplet rule. The primary distinction between an octet and a duplet is that an octet contains eight electrons in its outermost orbital while a duplet only has two.

Frequently Asked Questions-FAQs

What is Duplet rule with example?

According to the duplet rule, an element is stable if it has two electrons in its valence shell. For an element to reach this state, it must undergo electron loss, gain, or sharing, as well as the formation of chemical bonds. The duo rule is another name for this tenet. Only hydrogen, helium, and lithium are known to adhere to this criterion.

What is meant by octet rule?

According to the octet rule, atoms are at their most stable when their valence shells contain eight electrons.

Why do we use octet rule?

Because they constantly seek the most stable electron configuration, atoms adhere to the octet rule. The outermost energy level of an atom has fully filled s- and p-orbitals as a result of the octet rule. The first 20 elements in the periodic table, which have low atomic weights, are most likely to follow the octet rule.

Which follows octet rule?

The main group elements, such as oxygen, carbon, and nitrogen, follow octet laws. Except for lithium, hydrogen, and helium, all s-block and p-block elements adhere to the octet rule.

Why is octet inactive?

Due to its complete outer shell of electrons, an octet-shaped atom is not reactive.

Why do 8 electrons form a stable shell?

Because their electronic structure resembles that of the closest noble gas, atoms with 8 electrons in their valence shell have fully filled outermost orbitals and are consequently the most stable.

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6 thoughts on “What is the difference between Octet Rule and Duplet Rule”

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