Join thousands of students who trust us to help them ace their exams!Watch the first video
Multiple Choice
Which of the following best represents the correct Lewis dot structure for the neutral compound hydrogen cyanide (HCN)?
A
H–C=N with two lone pairs on nitrogen
B
H–C≡N with a lone pair on nitrogen
C
H–C–N with three lone pairs on nitrogen
D
H=C=N with one lone pair on nitrogen
Verified step by step guidance
1
Step 1: Determine the total number of valence electrons for the molecule 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.
Step 2: Arrange the atoms in a reasonable skeletal structure. Since hydrogen can only form one bond, it will be bonded to carbon, and carbon will be bonded to nitrogen, giving the sequence H–C–N.
Step 3: Use the total valence electrons to form bonds between the atoms. Start by placing single bonds between H and C, and between C and N. Then, add additional bonds (double or triple) between C and N to satisfy the octet rule for carbon and nitrogen.
Step 4: After forming the bonds, assign lone pairs to the atoms, especially nitrogen, to complete their octets. Remember that hydrogen only needs 2 electrons (a single bond) to be stable, while carbon and nitrogen need 8 electrons each.
Step 5: Verify the Lewis structure by checking that the total number of electrons used (bonding and lone pairs) equals the total valence electrons calculated in Step 1, and that all atoms have complete octets (except hydrogen). The correct structure for HCN has a triple bond between carbon and nitrogen and one lone pair on nitrogen.