How do you draw the Lewis structure of HCN?

HCN has 10 valence electrons. C is central, bonded to H and N. Two single bonds use 4 electrons; 6 remain. Place 3 lone pairs on N (6 e⁻). But C only has 4 electrons — not an octet.

Lewis Structure of HCN (Hydrogen Cyanide)

What is the Lewis structure of HCN?

HCN has 10 valence electrons, 4 bonding electron pairs, and 1 lone pair. HCN has 10 valence electrons. Two are in the H–C bond, six in the C≡N triple bond, and two form a lone pair on nitrogen. All atoms satisfy the octet/duet rule with formal charges of zero.

Lewis structure of HCN (Hydrogen Cyanide)

Formula	HCN
Name	Hydrogen Cyanide
Total Valence Electrons	10
Lone Pairs	1
Has Resonance	No
Concept	Multiple Bonds
Difficulty	Intermediate

Step 1: Count Valence Electrons

H has 1, C has 4, N has 5: 1 + 4 + 5 = 10 total.

Step 2: Draw the Skeleton

C is central, bonded to H and N. Two single bonds use 4 electrons; 6 remain.

Step 3: Distribute Lone Pairs

Place 3 lone pairs on N (6 e⁻). But C only has 4 electrons — not an octet.

Step 4: Form Multiple Bonds

Convert 2 lone pairs from N into bonding pairs: single → triple bond (C≡N). C now has 2 + 6 = 8 electrons. N keeps 1 lone pair + triple bond = 8.

Step 5: Check Formal Charges

C: FC = 4 - 0 - ½(8) = 0
N: FC = 5 - 2 - ½(6) = 0

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