Lewis structures of common molecules and ions
Every structure here is the one the Lewis Structure Generator draws, with its valence electrons, formal charges, resonance forms, VSEPR shape and polarity. Each formula opens a page with the drawing and the working.
Which molecules break the octet rule?
Of the 78 structures here, 9 leave an atom with fewer than eight electrons, among them BF₃, BeCl₂ and AlCl₃; 6 are radicals with an odd electron, such as NO and NO₂; and 19 give the central atom more than eight under the smallest formal charges convention, 11 of them under either convention.
Molecules 55
Neutral molecules whose central atom has at most eight electrons under the octets-first convention.
| Formula | Name | Valence electrons | Resonance forms | Shape | Octets | Polarity |
|---|---|---|---|---|---|---|
| H₂O | Water | 8 | 1 | bent | complete | polar |
| CO₂ | Carbon dioxide | 16 | 1 | linear | complete | nonpolar |
| CO | Carbon monoxide | 10 | 1 | linear, two atoms | complete | polar |
| NH₃ | Ammonia | 8 | 1 | trigonal pyramidal | complete | polar |
| CH₄ | Methane | 8 | 1 | tetrahedral | complete | nonpolar |
| O₃ | Ozone | 18 | 2 | bent | complete | polar |
| O₂ | Oxygen | 12 | 1 | linear, two atoms | complete | nonpolar |
| N₂ | Nitrogen | 10 | 1 | linear, two atoms | complete | nonpolar |
| H₂ | Hydrogen | 2 | 1 | linear, two atoms | complete | nonpolar |
| Cl₂ | Chlorine | 14 | 1 | linear, two atoms | complete | nonpolar |
| F₂ | Fluorine | 14 | 1 | linear, two atoms | complete | nonpolar |
| HCl | Hydrogen chloride | 8 | 1 | linear, two atoms | complete | polar |
| HF | Hydrogen fluoride | 8 | 1 | linear, two atoms | complete | polar |
| HCN | Hydrogen cyanide | 10 | 1 | linear | complete | polar |
| N₂O | Nitrous oxide | 16 | 1 | linear | complete | polar |
| NO | Nitric oxide | 11 | 1 | linear, two atoms | radical | polar |
| NO₂ | Nitrogen dioxide | 17 | 2 | bent | radical | polar |
| N₂O₄ | Dinitrogen tetroxide | 34 | 4 | trigonal planar at each N | complete | nonpolar |
| SO₂ | Sulfur dioxide | 18 | 1 | bent | expanded | polar |
| SO₃ | Sulfur trioxide | 24 | 1 | trigonal planar | expanded | nonpolar |
| H₂S | Hydrogen sulfide | 8 | 1 | bent | complete | polar |
| BF₃ | Boron trifluoride | 24 | 1 | trigonal planar | incomplete | nonpolar |
| BeCl₂ | Beryllium chloride | 16 | 1 | linear | incomplete | nonpolar |
| PCl₃ | Phosphorus trichloride | 26 | 1 | trigonal pyramidal | complete | polar |
| XeO₃ | Xenon trioxide | 26 | 1 | trigonal pyramidal | expanded | polar |
| CCl₄ | Carbon tetrachloride | 32 | 1 | tetrahedral | complete | nonpolar |
| CH₂Cl₂ | Dichloromethane | 20 | 1 | tetrahedral | complete | polar |
| CHCl₃ | Chloroform | 26 | 1 | tetrahedral | complete | polar |
| CH₂O | Formaldehyde | 12 | 1 | trigonal planar | complete | polar |
| C₂H₆ | Ethane | 14 | 1 | tetrahedral at each C | complete | nonpolar |
| C₂H₄ | Ethylene | 12 | 1 | trigonal planar at each C | complete | nonpolar |
| C₂H₂ | Acetylene | 10 | 1 | linear at each C | complete | nonpolar |
| H₂O₂ | Hydrogen peroxide | 14 | 1 | bent at each O | complete | depends |
| N₂H₄ | Hydrazine | 14 | 1 | trigonal pyramidal at each N | complete | depends |
| HNO₃ | Nitric acid | 24 | 2 | trigonal planar | complete | polar |
| HNO₂ | Nitrous acid | 18 | 1 | bent | complete | polar |
| H₂SO₄ | Sulfuric acid | 32 | 1 | tetrahedral | expanded | polar |
| H₃PO₄ | Phosphoric acid | 32 | 1 | tetrahedral | expanded | polar |
| HClO₄ | Perchloric acid | 32 | 1 | tetrahedral | expanded | polar |
| HOCl | Hypochlorous acid | 14 | 1 | bent | complete | polar |
| H₂CO₃ | Carbonic acid | 24 | 1 | trigonal planar | complete | polar |
| H₃PO₃ | Phosphorous acid | 26 | 1 | tetrahedral | expanded | polar |
| H₃PO₂ | Hypophosphorous acid | 20 | 1 | tetrahedral | expanded | polar |
| NF₃ | Nitrogen trifluoride | 26 | 1 | trigonal pyramidal | complete | polar |
| PH₃ | Phosphine | 8 | 1 | trigonal pyramidal | complete | polar |
| Cl₂O | Dichlorine monoxide | 20 | 1 | bent | complete | polar |
| C₂Cl₄ | Tetrachloroethylene | 36 | 1 | trigonal planar at each C | complete | nonpolar |
| AlCl₃ | Aluminum chloride | 24 | 1 | trigonal planar | incomplete | nonpolar |
| BH₃ | Borane | 6 | 1 | trigonal planar | incomplete | nonpolar |
| CH₃ | Methyl radical | 7 | 1 | trigonal planar | radical | nonpolar |
| OH | Hydroxyl radical | 7 | 1 | linear, two atoms | radical | polar |
| CH₂ | Methylene | 6 | 1 | bent | incomplete | polar |
| CF₂ | Difluorocarbene | 18 | 1 | bent | incomplete | polar |
| CCl₂ | Dichlorocarbene | 18 | 1 | bent | incomplete | polar |
| CBr₂ | Dibromocarbene | 18 | 1 | bent | incomplete | polar |
Ions 12
Charged species, the charge counted in the valence electrons, none of them needing more than eight round any atom.
| Formula | Name | Valence electrons | Resonance forms | Shape | Octets | Polarity |
|---|---|---|---|---|---|---|
| BF₄⁻ | Tetrafluoroborate ion | 32 | 1 | tetrahedral | complete | not applicable |
| NO₂⁺ | Nitronium ion | 16 | 1 | linear | complete | not applicable |
| NO⁺ | Nitrosonium ion | 10 | 1 | linear, two atoms | complete | not applicable |
| NH₂⁻ | Amide ion | 8 | 1 | bent | complete | not applicable |
| CH₃⁺ | Methyl cation | 6 | 1 | trigonal planar | incomplete | not applicable |
| O₂⁻ | Superoxide ion | 13 | 2 | linear, two atoms | radical | not applicable |
| AlH₄⁻ | Tetrahydroaluminate ion | 8 | 1 | tetrahedral | complete | not applicable |
| BH₄⁻ | Borohydride ion | 8 | 1 | tetrahedral | complete | not applicable |
| C₂²⁻ | Acetylide ion | 10 | 1 | linear, two atoms | complete | not applicable |
| S₂²⁻ | Disulfide ion | 14 | 1 | linear, two atoms | complete | not applicable |
| BO₂⁻ | Metaborate ion | 16 | 1 | linear | complete | not applicable |
| NH₃⁺ | Ammonia radical cation | 7 | 1 | trigonal planar | radical | not applicable |
Hypervalent molecules and ions 11
The central atom holds more than eight electrons whichever convention is used, which only atoms from period 3 on can do.
| Formula | Name | Valence electrons | Resonance forms | Shape | Octets | Polarity |
|---|---|---|---|---|---|---|
| PCl₅ | Phosphorus pentachloride | 40 | 1 | trigonal bipyramidal | expanded | nonpolar |
| SF₄ | Sulfur tetrafluoride | 34 | 1 | see-saw | expanded | polar |
| SF₆ | Sulfur hexafluoride | 48 | 1 | octahedral | expanded | nonpolar |
| ClF₃ | Chlorine trifluoride | 28 | 1 | T-shaped | expanded | polar |
| BrF₅ | Bromine pentafluoride | 42 | 1 | square pyramidal | expanded | polar |
| XeF₂ | Xenon difluoride | 22 | 1 | linear | expanded | nonpolar |
| XeF₄ | Xenon tetrafluoride | 36 | 1 | square planar | expanded | nonpolar |
| XeF₆ | Xenon hexafluoride | 50 | 1 | distorted octahedral | expanded | no estimate |
| IF₇ | Iodine heptafluoride | 56 | 1 | pentagonal bipyramidal | expanded | nonpolar |
| I₃⁻ | Triiodide ion | 22 | 1 | linear | expanded | not applicable |
| ICl₄⁻ | Tetrachloroiodate ion | 36 | 1 | square planar | expanded | not applicable |
In the Octets column, complete means every atom but H has eight electrons; incomplete, that an atom is left with fewer; expanded, that an atom from period 3 on holds more; and radical, that an electron is unpaired. Polarity is the generator’s estimate from the VSEPR shape and the electronegativities, and it is not given for an ion.
To draw any other molecule or ion, type it into the Lewis Structure Generator, which builds the structure one step at a time. The VSEPR Molecular Geometry viewer turns each shape in 3D.