1
Parse the molecular formula
HCN -> H, C, N
The molecule contains hydrogen, carbon, and nitrogen.
Lewis Structure
HCN Lewis Structure
Hydrogen cyanide
HCN is drawn as H-C triple bonded to N, with one lone pair on nitrogen.
Use the diagram and steps below to check the hydrogen cyanide Lewis structure, HCN Lewis dot structure, valence electrons, formal charges, and molecular shape.
HCN
Hydrogen cyanide
Valence electrons10
Central atomC
GeometryLinear
Bond angle180 deg
PolarityPolar
Electron geometryLinear
VSEPR Geometry
Molecular geometry
Linear
Electron geometry
Linear
Bond angle
180 deg
Polarity
Polar
Valence electrons
10
Bonding / lone pairs
2 / 0 around C
Central atom
C
Electron regions
2
How to Draw HCN: Step-by-Step
2
Count total valence electrons
1 + 4 + 5 = 10
Add the valence electrons from H, C, and N.
3
Choose the central atom
Skeleton: H-C-N
Hydrogen must be terminal. Carbon can connect hydrogen and nitrogen.
4
Form a multiple bond
H-C triple bond N
A C-N triple bond gives carbon and nitrogen full octets.
5
Place the lone pair
One lone pair on N
The remaining 2 electrons are placed on nitrogen.
6
Final answer
The HCN Lewis structure is H-C triple bond N with one lone pair on nitrogen.
Formal Charges
| Atom | Formal charge |
|---|---|
| H | 0 |
| C | 0 |
| N | 0 |
Common Mistakes
- Hydrogen cannot be central.
- A single C-N bond does not give carbon and nitrogen enough electrons.
FAQ
What is the Lewis structure for HCN?
The HCN Lewis structure is H-C triple bond N with one lone pair on nitrogen.
What is the Lewis dot structure for HCN?
The Lewis dot structure for HCN is the electron-dot drawing shown above. The HCN Lewis structure is H-C triple bond N with one lone pair on nitrogen.
How many valence electrons does HCN have?
HCN has 10 total valence electrons in this Lewis structure.
What is the molecular geometry of HCN?
HCN has linear molecular geometry and linear electron geometry.
Is HCN polar or nonpolar?
HCN is polar in the Lewis structure shown here. Its molecular geometry is Linear.
References
Method notes are aligned with standard Lewis structure steps: count valence electrons, draw a skeleton, distribute electrons, form multiple bonds when needed, and check formal charges and resonance.
OpenStax Chemistry 2e: Lewis Symbols and Structures and Formal Charges and Resonance.