what are the postulates of Lewis approach?
Answers
Kossel-Lewis approach to Chemical Bonding
W.Kossel laid down the following postulates to the understanding of ionic bonding:
1. In the periodic table, the highly electronegative halogens and the highly electropositive alkali metals are separated by the noble gases. Therefore one or small number of electrons are easily gained and transferred to attain the stable noble gas configuration.
2. The formation of a negative ion from a halogen atom and a positive ion from an alkali metal atom is associated with the gain and loss of an electron by the respective atoms.
3. The negative and positive ions so formed attains stable noble gas electronic configurations. The noble gases (with the exception of helium which has two electrons in the outermost shell) have filled outer shell electronic configuration of eight electrons (octet of electrons) with a general representation ns2 np6.
4. The negative and positive ions are bonded and stabilised by force of electrostatic attraction.
Kossel's postulates provide the basis for the modern concepts on electron transfer between atoms which results in ionic or electrovalent bonding.
For example, formation of NaCl molecule from sodium and chlorine atoms can be considered to take place according to Kossel's theory by an electron transfer as:
(i) Na ( [Ne] 3s1) -- loss of e --- > Na+ + e ( [Ne])
where [Ne] = electronic configuration of Neon
(ii) Cl + e ([Ne]3s2 3p5 ) - gain of e -- > Cl-1([Ar])
[Ar] = electronic configuration of ArgonKossel-Lewis approach to Chemical Bonding
W.Kossel laid down the following postulates to the understanding of ionic bonding:
1. In the periodic table, the highly electronegative halogens and the highly electropositive alkali metals are separated by the noble gases. Therefore one or small number of electrons are easily gained and transferred to attain the stable noble gas configuration.
2. The formation of a negative ion from a halogen atom and a positive ion from an alkali metal atom is associated with the gain and loss of an electron by the respective atoms.
3. The negative and positive ions so formed attains stable noble gas electronic configurations. The noble gases (with the exception of helium which has two electrons in the outermost shell) have filled outer shell electronic configuration of eight electrons (octet of electrons) with a general representation ns2 np6.
4. The negative and positive ions are bonded and stabilised by force of electrostatic attraction.
Kossel's postulates provide the basis for the modern concepts on electron transfer between atoms which results in ionic or electrovalent bonding.
For example, formation of NaCl molecule from sodium and chlorine atoms can be considered to take place according to Kossel's theory by an electron transfer as:
(i) Na ( [Ne] 3s1) -- loss of e --- > Na+ + e ( [Ne])
where [Ne] = electronic configuration of Neon
(ii) Cl + e ([Ne]3s2 3p5 ) - gain of e -- > Cl-1([Ar])
[Ar] = electronic configuration of Argon
hope it helps ❤️
Answer:
Postulates of Kossel- Lewis electronic theory of valency:
1. According to this theory , atoms combine either by transfer of valence electrons from one atom to another or by sharing of valence electrons in order to acquire octet in its valence shell.
2. An ionic bond is formed by the transfer of electrons between two atoms. The atom which lose electron/s and the atom which gains electron/s can achieve octet in their valence shell.
3. A covalent bond is formed by sharing of electrons between the two atoms. Atoms can achieve octet in their valence shell by sharing one , two or three electrons from each atom.
The octet rule or the electronic theory of chemical bonding was developed by Kossel and Lewis. According to this rule, atoms can combine either by transfer of valence electrons from one atom to another or by sharing their valence electrons in order to attain the nearest noble gas configuration by having an octet in their valence shell.