Question

Which of the following molecules has two sigma ($\sigma$) and two pi ($\pi$) bonds?

• A. $N_2$
• B. $C_2H_6$
• C. $N_2F_2$
• D. HCN
• E. $C_2H_2Cl_2$

Hint:

Triple bonds consist of one sigma and two pi bonds.

Answer 1

The Correct Option is D

Step 1: Sigma ($\sigma$) bonds are single bonds, while pi ($\pi$) bonds are additional bonds in double or triple bonds. 
Step 2: Analyzing each molecule: 
$N_2$ has 1 $\sigma$ and 2 $\pi$ bonds. 
$C_2H_6$ has only $\sigma$ bonds. 
$N_2F_2$ has only $\sigma$ bonds. 
$HCN$ has a triple bond between C and N, meaning 1 $\sigma$ and 2 $\pi$ bonds between them. Additionally, a $\sigma$ bond exists between H and C. 
$C_2H_2Cl_2$ has different bonding but does not match the criteria. 
Step 3: Since HCN has exactly 2 sigma bonds and 2 pi bonds, the correct answer is (D).