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Kossel-Lewis Approach To Chemical Bond

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Kossel-Lewis Approach To Chemical Bond - Lesson Summary

In the nature, the system with more energy is less stable. In other words, the lowest energy state corresponds to the most stable state of the system.

So every system tends to attain stability by losing energy.

Kossel and Lewis developed electronic theory of valence or theory of chemical bonding to explain the formation of chemical bond between the two atoms.

According to the electronic theory of valence, every atom tries to attain octet configuration (presence of eight electrons) in its valence shell by losing or gaining or by sharing of electrons. This is known as the "Octet Rule".

The electrostatic forces of attraction that holds the two oppositely charged ions together are known as "electrovalent bond".

Atoms attain stability by the means of bond formation. The process of bond formation is associated with the lowering of energy of the system.

Only valence electrons participate in chemical bonding, but not inner electrons.

To understand the concept of valence electrons Lewis introduced the concept representing valence electrons with dots, which are called Lewis symbols.

Importance of Lewis symbols:

They provide the number of outer most or valence electrons around the atom.

With the help of number of valence electrons it is easy to calculate valency of the atom.

Following has given the Lewis symbols for the elements of 2nd period.

Lewis symbol for Chlorine atom.

Kossel approach towards chemical bonding:
Halogens are highly electronegative elements and alkali metals are most electropositive elements in the periodic table.

Halogens in the process of getting stability gains electrons and attain negative charge.

X + e⁻ → X⁻

And alkali metals will lose electrons in the process of attaining stability will get positive charge.

M -e⁻ → M⁺

During these processes the halogens and alkali metals acquire the octet configuration and even duplet configuration.

And there exist electrostatic force of attraction between these negative and positive charges. This is called as electrovalent bond.


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