Chemistry Class 11 NCERT Solutions: Chapter 4 Chemical Bonding and Molecular Structure Part 3 (For CBSE, ICSE, IAS, NET, NRA 2023)

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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

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

(B)

Image Showing Resonance Strcuture of NO2

(C)

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

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

(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

(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

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

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