Q. According to the Valence bond theory, which statement is incorrect regarding bonding between two carbon atoms?

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A sigma(σ) bond is weaker than a Pi $\text{(\pi )}-\text{b}\text{o}\text{n}\text{d}$

A sigma bond is stronger than a Pi bond.

A double bond is stronger than a single bond

A double bond is shorter than a single bond

Solution:

A $\text{σ}-$ bond is stronger than a $\text{\pi }-$ bond.
Sigma $\left(\text{σ}\right)$ bonds are formed by head-on overlap of unhybridised $s-s, \, p-p \, or \, s-p$ orbitals and hybridized orbitals $\left(sp , \, \left(sp\right)^{2} , \, \left(sp\right)^{3} , \, \left(sp\right)^{3} d \, and \, \left(sp\right)^{3} d^{2}\right)$ . Hence, $\text{σ}$ bond are strong bonds. Where as Pi $\left(\text{\pi }\right)-$ bonds are formed by side-wise overlap of unhybridised p and d orbitals. Hence $\text{\pi }$ bonds are weak bonds.

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