Question

Number of $\sigma$ and $\pi$ bonds in $C_2$ molecule is/are:

• A. $1\sigma$ and $1\pi$
• B. $1\sigma$ and $2\pi$
• C. $2\pi$ only
• D. $1\sigma$ and $3\pi$

Answer 1

The correct option is C $2\pi$ only

$C_2$ molecules have been found in vapour state. Their double bonds are made of two pi bonds because four electrons need to be accomodated in each bond. So this is against the rule that there must be a sigma bond before a pi bond is formed in the double bond.
Conclusion: hence the answer option (c) is correct.