LEWIS STRUCTURE RULES
1. Place the least electronegative atom (that isn’t hydrogen) in the middle. Join the remaining atoms with single bonds. e.g. In HNO
2
you’d put N in the middle
2. Sum the valence electrons (including or excluding those involved in ionic charge). e.g. H 1, O 6, N 5, O 6 = 18 valence electrons
3. Count the electrons already committed to forming the single bond skeleton. i.e. in this case there are 3 single bonds or 6 bonding electrons
4. Count the number of electrons that would be required to fulfill the octet rule. i.e., in this case 14 electrons, but only 12 electrons are available (18 minus 6)
5. Add a multiple bond for each pair of electrons that are deficient. In this case, we have one multiple bond.
6. On each atom, make up the octet of electrons with lone pairs. If more than 1 structure is possible (i.e., resonance structures), assign formal charges to narrow down the options.
Hints for Drawing Lewis Structures
1. Consider only valence electrons (neglect the inner electrons).
2. H atoms only form single bonds
3. C, N, O, F nearly always obey the octet rule.
C always has 4 bonds (exception CO); N can have 3 or 4 bonds; O has 2 or 1 bond; F has 1 bond
4. O-O bonds are rare, e.g. H2O2 hydrogen peroxide H-O-O-H
5. In oxyacids, the H atom is normally joined to an O atom.
LEWIS STRUCTURE RULES
1. Place the least electronegative atom (that isn’t hydrogen) in the middle. Join the remaining atoms with single bonds. e.g. In HNO
2
you’d put N in the middle
2. Sum the valence electrons (including or excluding those involved in ionic charge). e.g. H 1, O 6, N 5, O 6 = 18 valence electrons
3. Count the electrons already committed to forming the single bond skeleton. i.e. in this case there are 3 single bonds or 6 bonding electrons
4. Count the number of electrons that would be required to fulfill the octet rule. i.e., in this case 14 electrons, but only 12 electrons are available (18 minus 6)
5. Add a multiple bond for each pair of electrons that are deficient. In this case, we have one multiple bond.
6. On each atom, make up the octet of electrons with lone pairs. If more than 1 structure is possible (i.e., resonance structures), assign formal charges to narrow down the options.
Hints for Drawing Lewis Structures
1. Consider only valence electrons (neglect the inner electrons).
2. H atoms only form single bonds
3. C, N, O, F nearly always obey the octet rule.
C always has 4 bonds (exception CO); N can have 3 or 4 bonds; O has 2 or 1 bond; F has 1 bond
4. O-O bonds are rare, e.g. H2O2 hydrogen peroxide H-O-O-H
5. In oxyacids, the H atom is normally joined to an O atom.