Which of the following best describes the correct Lewis dot structure for the neutral compound HCN?

• A. H–C–N, with single bonds between all atoms and three lone pairs on N
• B. H–C=N, with a single bond between H and C, a double bond between C and N, and two lone pairs on N
• C. H–C≡N, with a single bond between H and C, a triple bond between C and N, and a lone pair on N
• D. H=C=N, with a double bond between H and C, a single bond between C and N, and one lone pair on N

Answer: (C)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons in HCN. Hydrogen (H) has 1 valence electron, Carbon (C) has 4, and Nitrogen (N) has 5. Add these together to get the total valence electrons available for bonding.
2. Step 2: Arrange the atoms with Carbon as the central atom because it can form multiple bonds, placing Hydrogen on one side and Nitrogen on the other.
3. Step 3: Connect the atoms with single bonds initially: H–C–N. Each single bond represents 2 electrons. Subtract these bonding electrons from the total valence electrons to find how many electrons remain for lone pairs or multiple bonds.
4. Step 4: Distribute the remaining electrons to satisfy the octet rule for Carbon and Nitrogen. Since Hydrogen only needs 2 electrons, focus on completing octets for C and N. Consider forming double or triple bonds between C and N if needed to complete their octets.
5. Step 5: Evaluate the formal charges on each atom to ensure the most stable Lewis structure. The best Lewis structure will have formal charges closest to zero and satisfy the octet rule, which leads to a triple bond between C and N, a single bond between H and C, and one lone pair on Nitrogen.