Chemistry Class 11 NCERT Solutions: Chapter 4 Chemical Bonding and Molecular Structure Part 3

Q: 12. Equation can be represented by structures 1 and 2 shown below. Can these two structures be taken as the canonical forms of the resonance hybrid representing Equation If not, give reasons for the same.

Image showing structure of H3PO3.

Image Showing Structure of H3PO3.

Image showing structure of H3PO3.

Answer: The given structures cannot be taken as the canonical forms of the resonance hybrid of Equation because the positions of the atoms have changed.

Q: 13. Write the resonance structures for Equation .

Answer:

The resonance structures are:

(A) Equation

Image showing resonance strcuture of SO3.

Image Showing Resonance Strcuture of SO3.

Image showing resonance strcuture of SO3.

(B) Equation

Image showing resonance strcuture of NO2.

Image Showing Resonance Strcuture of NO2.

Image showing resonance strcuture of NO2.

(C) Equation

Image showing resonance structure of NO3-.

Image Showing Resonance Structure of NO3-.

Image showing resonance structure of NO3-.

Q: 14. Use Lewis symbols to show electron transfer between the following atoms to from cations and anions:

(A) K and S

(B) Ca and O

(C) Al and N

Answer:

(A) K and S:

The electronic configurations of K and S are as follows:

K: 2, 8, 8, 1

S: 2, 8, 6

Image showing electronic configurations of K and S.

Image Showing Electronic Configurations of K and S.

Image showing electronic configurations of K and S.

Sulphur (S) requires 2 more electrons to complete its octet. Potassium (K) requires one electron more than the nearest noble gas i.e., Argon. Hence, the electron transfer can be shown as:

Image showing electron transfer of Sulphur.

Image Showing Electron Transfer of Sulphur.

Image showing electron transfer of Sulphur.

(B) Equation

The electronic configurations of Ca and O are as follows:

Equation

Equation

Oxygen requires two electrons more to complete its octet, whereas calcium has two electrons more than the nearest noble gas i.e., Argon. Hence, the electron transfer takes place as:

Image showing electron transfer of Ca and O.

Image Showing Electron Transfer of Ca and O.

Image showing electron transfer of Ca and O.

(C) Al and N:

The electronic configurations of Al and N are as follows:

Equation

Equation

Nitrogen is three electrons short of the nearest noble gas (Neon), whereas aluminium has three electrons more than Neon. Hence, the electron transference can be shown as:

Image showing electron transfer of Al and N

Image Showing Electron Transfer of Al and N

Image showing electron transfer of Al and N

Q: 15. Although both Equation and Equation are triatomic molecules, the shape of Equation molecule is bent while that of Equation is linear. Explain this on the basis of dipole moment.

Answer:

According to experimental results, the dipole moment of carbon dioxide is zero. This is possible only if the molecule is linear so that the dipole moments of C-O bonds are equal and opposite to nullify each other.

Image showing Lewis structure of CO2.

Image Showing Lewis Structure of CO2.

Image showing Lewis structure of CO2.

Resultant Equation

Equation on the other hand, has a dipole moment value of Equation D (though it is a triatomic molecule as Equation ).

The value of the dipole moment suggests that the structure of Equation molecule is bent where the dipole moment of O-H bonds are unequal.

Image showing Lewis structure of H2O.

Image Showing Lewis Structure of H2O.

Image showing Lewis structure of H2O.

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