11 Class Chapter 4- Chemical Bonding and Molecular Structure

These are chemistry notes of chapter Chemical Bonding and Molecular Structure Class 11th.

Chemical Bonding and Molecular Structure Class 11

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
 
·        End O atom marked as 3

 

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