Lewis structures
A Lewis structure of a compound indicates the number of valence electrons associated with each component atom. A pair of electrons that is shared between two atoms is represented by a single line (single bond), sharing of two pairs of electrons is represented by two lines (double bond) and sharing of three pairs of electrons is represented by three lines (triple bond). Dots placed on an atom represent non-bonding valence electrons, which are usually in pairs with opposing spins (lone pairs). Core electrons are not indicated. A five-step procedure applies for drawing Lewis structures:
- Determine the number of valence electrons for each atom type.
- Draw the bonding framework with single bonds between atoms
- Place three non-bonding pairs of electrons on all outer atoms except hydrogen.
- Assign the remaining valence electrons to the central atom.
- Minimise formal charges on all atoms.
Note: Molecular ions can also be represented by Lewis structures.