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

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Q: 12. 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 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 because the positions of the atoms have changed.

Q: 13. Write the resonance structures for .

Answer:

The resonance structures are:

(A)

Image showing resonance strcuture of SO3.

Image Showing Resonance Strcuture of SO3.

Image showing resonance strcuture of SO3.

(B)

Image showing resonance strcuture of NO2.

Image Showing Resonance Strcuture of NO2.

Image showing resonance strcuture of NO2.

(C)

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)

The electronic configurations of Ca and O are as follows:

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:

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 and are triatomic molecules, the shape of molecule is bent while that of 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

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

The value of the dipole moment suggests that the structure of 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.