8.2 Lewis Dot Structures

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Octet Rule

Atoms will typically transfer or share electrons in an attempt to have 8 electrons around them.

OCTET RULE EXCEPTIONS
1. A few atoms routinely go under the octet rule H only 2 Be only 4 B and Al only 6
2. Third row and lower can exceed the octet rule
3. Molecules with odd numbers of electrons (ex. NO)

RULE FOR DRAWING LEWIS STRUCTURES
1	Set up skeleton with single bonds (central atom is the atom which can make the most bonds).
2	Fill the octets of the outside atoms with lone pairs of electrons.
3	Any remaining valence electrons go on the central atom.
4	Once all electrons are used, form multiple bonds to central atom if not “full.”

Formal Charge = Number of Valence e^- – [Nonbonding e^- + ½ bonding e^-]

Formal Charge = Number of Valence e^- – [“dots” + “lines”]

Rules for Best Formal Charges
1. Fewer formal charges
2. Lower magnitude (closer to zero)
3. Negative charge on more electronegative atom

Resonance – involves the delocalization of electrons

– Affects the bond length and strength