Question

Give reasons for the following:

A) Covalent bonds are directional bonds while ionic bonds are non- directional.

Give reasons for the following:

B) Water molecule has bent structure whereas carbon dioxide molecule is linear.

Give reasons for the following:

C) Ethyne molecule is linear

Answer 1

A) A covalent bond is formed when specific orbitals of one atom combines with orbitals of other atom i.e., merging/ overlap of orbital is the cause of covalent bond formation. The orbitals need to be aligned in specific directions to merge constructively. That's why covalent bonds are directional.

The lonic bond is formed when the electron transfer occurs from one atom to other. lonic/Electrostatic field attractions of positive or negative ions are equal in all directions, so, ionic bond is non-directional or omnidirectional in nature.

B) Analysis of concept of Hybridization

Hybridization is the the process of intermixing of the orbitals of slightly different energies, so as to redistribute their energies,which results in the formation of new set of orbitals of equivalent energies and shape.

Hybridization helps in deciding the structure of the molecules.

Electron pair types:

* Lone pair (lp)

* Bond pair (bp)

Total number of hybrid orbitals = No. of lone pairs on central atom + No. of bond pairs (i.e. given by No. of sigma bonds made by central atom)

Using the hybridization concept to find their structure


Conclusion-

So, due to different hybridizations, $i.e"s{p}^3"$ for water (give rise to bent structure due to 2 lone pairs) and "sp" for carbon dioxide (give rise to linear structure), they have different shapes.


C) Structure of ethyne

$HC\equiv CH$

Here lone pair of electron on carbon atom = 0

No. of sigma bonds formed by each carbon = 2;

Total number of hybrid orbitals =No. of lone pairs on central atom + No. of sigma bonds made by central atom

So, total number of hybrid orbitals = 0+2=2

Thus, hybridisation of C in ethyne $i.e.,C_2{H}_2$ is sp.

One sp hybrid orbital of one carbon atom overlaps axially with sp hybrid orbital of the other carbon atom to form C-C sigma bond while the other hybridized orbital of each carbon atom overlaps axially with S orbitals of hydrogen atoms forming $\sigma$ bonds.

Unhybridised orbitals form $\pi$ bonds

Hence, the structure of ethyne is Linear with a bond Angle of ${180}^{\circ }$