Chemical Bonding and Molecular Structure
Attractive force which held’s various constituents
(like atoms, ions etc.) together in difference chemical species is known as a
chemical bond.
Kossel Lewis Approach to Chemical Bonding: -
Lewis discussed that atoms achieve stable octet when they linked by chemical bonds.
·
In
NaCl, an electron transfer from
Na to Cl and give Na+ and Cl- ions and ,
·
In case of Cl2,H2,F2, sharing of electron takes place to complete
stable outer octet.
·
Valence electrons take part in chemical
reaction or combination.
·
Symbol to represent valence electron in
atom is known as Lewis symbol.
Example:-
· Significance of Lewis symbol :-
To
calculate valence = (no. Of dots and or / eight minus no. Of dots)
Octet rules :-
According to this rule , atoms can combine either by sharing electron or by transfer (gaining or losing ) of electron to complete octet (i.e. 8 electron in outer most shell).Covalence bond :-
Bond forms by sharing of electrons.
·
When sharing of one pair of electron
takes place is known as single covalent bond.
·
When sharing of two pair of electrons
takes place is known as double bond.
·
When sharing of three pair of electron
takes place is known as triple bond.
Formal charge (F.C.) : -
For polyatomic molecule or ion, formal charge of an
atom in a Lewis structure = [Total no. of Valence electron in free Atom] -
[total no. of non bonding (lone- pair) elements]- 1/2[total no of bonding
(shared) electrons]
Ex :- Lewis structure of O3 (ozone
molecule)
Atoms in O3 is marked as 1,2,3
·
Central
O atom marked as 1
·
Central
O atom marked as 2
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