What is electronic theory of chemical bonding?
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What is electronic theory of chemical bonding?
Aug 26, 2022, 16:45 IST
Electronic theory of valence of chemical bond:
This theory was proposed by W. Kossel and G.N.Lewis (1916) . It was based on the electronic configuration of the elements and Bohr’s atomic structure. This theory is also known as chemical bond theory. Kossel explained the formation of ionic bond while Lewis explained the formation of covalent bond.
Important postulates of this theory are given below:
1. Valency of an atom depends mainly on the number of electrons present in the outermost orbit. These electrons are termed as valency electrons.
2. Electronic configuration of noble gases is stable (ns 2 np 6 ) i.e., eight electrons are present in the outer most orbit except helium having two electrons. These gases are chemically inert and do not form compounds.
Physics Wallah Chemistry Doubts page consist of more questions for reference.
|
Noble gas |
Atomic Number |
Electronic Configuration |
|
Helium (He) |
2 |
2 (duplet) |
|
Neon (Ne) |
10 |
2, 8 (octet) |
|
Argon (Ar) |
18 |
2, 8, 8 (octet) |
|
Krypton (Kr) |
36 |
2, 8, 18, 8 (octet) |
|
Xenon (Xe) |
54 |
2, 8, 18, 18, 8 (octet) |
|
Radon (Rn) |
86 |
2, 8, 18, 32, 18, 8 (octet) |
Even though He, has two electrons, it is highly stable and chemically inert.
1.Elements, other than zero group elements are chemically active because they have less than eight electrons in their outer most orbit.
eg . Na (2, 8, 1), Cl (2, 8, 7)
The number of electrons which take part in a chemical combination determines the valency of the atoms.
1. Every atom, therefore, tries to acquire the stable electronic configuration in its outermost orbit as in the zero group elements in periodic table (except H, Li, Be).
2. Therefore, this stable configuration ns 2 np 6 (octet), ns 2 (duplet) is attained either by losing, gaining or sharing of electrons during bond formation.
Octet Rule: An atom must possess eight electrons in its outermost orbit for its stability. BeCl 2 , BF 3 , AlCl 3 , PCl 5 , SF 6 , XeF 2 , XeF 4 , XeF 6, etc, the molecules do not obey the octet rule.
Duplet Rule: H, Li, Be, B etc attain stable nearest noble gas configuration i.e., two electron in their outer most orbit like He.
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