Chemistry Class-11: Chapter –4. Chemical Bonding and Molecular Structure Part-9

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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:

and for oxygen and fluorine order of energy of molecular orbitals is given below:

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’, and if the overlap is lateral, the molecular orbital is called ‘pi’, . 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.

Question: 65

Which of the following statements is correct?

(i) In the formation of dioxygen from oxygen atoms 10 molecular orbitals will be formed.

(ii) All the molecular orbitals in the dioxygen will be completely filled.

(iii) Total number of bonding molecular orbitals will not be same as total number of anti bonding orbitals in dioxygen.

(iv) Number of filled bonding orbitals will be same as number of filled anti bonding orbitals.

Answer: (i)

Question: 66

Which of the following molecular orbitals has maximum number of nodal planes?

(i)

(ii)

(iii)

(iv)

Answer: (ii)

Question: 67

Which of the following pair is expected to have the same bond order?

(i)

(ii)

(iii)

(iv)

Answer: (ii)

Question: 68

In which of the following molecules, molecular orbital is filled after and molecular orbitals?

(i)

(ii)

(iii)

(iv)

Answer: (iii)

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