How to Draw Lewis Structures

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How to Draw Lewis Structures

Lewis Structures are a rite of passage in general chemistry courses. This is because they tell us about the arrangement of valence electrons in the molecule. From this we can predict the shape, reactivity, polarity ... and other important information about the molecule.

Rules for Lewis Structures

These general rules help write correct Lewis Structures:

  • Step 1: Count the number of valence electrons for the molecule.

  • Step 2: Write a skeleton structure of the molecule. The least electronegative element goes in the center.

  • Step 3: Place a pair or electrons between atoms to form bonds.

  • Step 4: Complete the octets for atoms using the remaining valence electrons.

  • Step 5: Check that you only used the number of valence electrons in Step 1. If not, you may need double or triple bonds.

Beware of exceptions to the Octet Rule!

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