Long Answer TypeDiscuss the orbital shapes of the following covalent molecules:
(i) HF (ii) H2O (iii) NH3.
Short Answer TypeLong Answer TypeUsing the orbital overlap concept, explain the formation of:
(i) O2 molecule (ii) N2 molecule.
Distinguish between a sigma 
bond and a 
bond.
| Sigma (σ) bond | pi  bond |
| 1. It is formed by the coaxial over lapping of two half filled atomic orbitals along inter-nuclear axis | It is formed by the sidewise or lateral overlapping of two half filled p-orbitals perpendicular to the internuclear axis. |
| 2. This bond can be formed by overlap of s –s.s –p and p-p orbitals. | 2. It involves the overlap of p-orbitals only i.e. s orbitals can not participate in the formation of  bond. |
| 3. Sigma bond is stronger and less reactive. | 3.  bond is weaker and more reactive. |
| 4. They have cylindrical symmetry of electron density about the bond axis. | 4. Electron density is localised above and below the plane of bond axis. |
| 5. Free rotation about a σ-bond is possible. | 5. Rotation of bond is restricted. |
| 6. Sigma bonds have independent existence. | 6.  -bonds exist along with a σ bond. |
What is coordinate or dative bond? Explain the formation of the bond with some examples.
Short Answer TypeLong Answer Type
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