Solution of Chapter 4. Chemical Bonding and Molecular Structure (Chemistry - Exemplar Book)

Chapter Exercises

Multiple Choice Questions I

Multiple Choice Questions II

Short Answer

Matching Type

Assertion and Reason

Long Answer


(i)Discuss the concept of hybridization. What are its different types in a carbon atom?

(ii) What is the type of hybridisation of carbon atoms marked with star.

Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option.

Molecular orbitals are formed by the overlap of atomic orbitals. Two atomic orbitals combine to form two molecular orbitals called bonding molecular orbital (BMO) and anti bonding molecular orbital (ABMO). Energy of anti bonding orbital is raised above the parent atomic orbitals that have combined and the energy of the bonding orbital is lowered than the parent atomic orbitals. Energies of various molecular orbitals for elements hydrogen to nitrogen increase in the order :

σσ < σ *1s < σ2s < (π2px = π2py) < σ2p2 < σ2pz < (π * 2px = π*2py) < σ* 2pz s ( p p) p ( * p * p) * p < and for oxygen and fluorine order of energy of molecular orbitals is given below :

σls < σ* 1s < σ2s < σ* 2s < σ2pz < (π2px = π2py) < (π* 2px = π * 2py) < σ* 2pz

Different atomic orbitals of one atom combine with those atomic orbitals of the second atom which have comparable energies and proper orientation. Further, if the overlapping is head on, the molecular orbital is called ‘Sigma’, (σ) and if the overlap is lateral, the molecular orbital is called ‘pi’, (π). The molecular orbitals are filled with electrons according to the same rules as followed for filling of atomic orbitals. However, the order for filling is not the same for all molecules or their ions. Bond order is one of the most important parameters to compare the strength of bonds.