Chemical Bonding

Question 4. Distinguish between a sigma bond and a Pi bond.

Answer.

Sigma bond

1. A sigma bond is formed between two atoms by linear overlapping of partially filled atomic orbitals.

2. Overlapping orbitals can be pure orbitals ( i. e. s-s, p-p), hybrid orbitals (i. e. sp3-sp3, sp2-sp2, sp-sp) or pure and hybrid oribital (i. e. s-sp etc)

3. Overlapping of atomic orbitals is more in sigma bond than in pi bond, so bond energy of sigma bonds are also greater than that of pi bond.

4. Sigma bonds exist independently

5. In sigma bond, probability of finding electrons is maximum around bond axis.

6. Sigma bond is stronger than pi bond.

7. Sigma bond allows free rotation around it.

8. Sigma bond determines the geometry of molecule.

Pi bond

1. A Pi bond is formed between two atoms by parallel overlapping of partially filled atomic orbitals.

2. Overlapping orbitals are pure orbitals ( i. e. p-p).

3. Overlapping of atomic orbitals is lesser in pi bond than in sigma bond, so bond energy of pi bond is also lesser than of sigma bond.

4. Pi bond cannot exist independently. It is only formed if sigma bond is already formed.

5. In pi bond, probability of finding electrons is maximum above and below the bond axis.

6. Pi bond is weaker than sigma bond.

7. Pi bond does not allow free rotation around it.

8. Pi bond cannot determine the geometry of molecule.

Also Read: A double bond is stronger than single and tripple bond is stronger double bond, explain.

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