Rebel Molecules

MOST OF THE TIME THE OCTET RULE IS FOLLOWED, ome molecules disobey octet rule C, N, O, and F are mostly rule keepers 1) Odd Number of Valence Electrons 2) Incomplete Octets 3) Expanded Valence Shells

Not every electron is in a pair All atoms in the molecule cannot have their octet satisfied These molecules are generally NOT stable CHECK electron number before assuming odd number of electrons Ex. NO, NO 2

Molecules with odd valence electron #, not stable Very reactive Intermediate compounds in a chemical reaction, short-living

Not enough valence electrons to go around ! Not every atom can achieve the octet rule as a result Reactive 1 st share single electron pair and then if necessary, it is possible to satisfy the octet rule for ALL atoms by sharing 2-3 electron pairs Atoms with strong double/triple bonds are C, N, O, P, and S.

GENERALLY, A) All Lewis Structures are not necessarily equal for resonance hybrid B) Some resonance structures contribute more to the structure of the resonance hybrid than others.

Applies only to elements in 3+ periods of periodic table Central atom’s valence shell expands to account for extra electrons

**Applies only to elements in 3+ periods of periodic table ** ** Applied when not possible to draw Lewis structure without expanding the shells ** Valence shell incorporates “d subshell region” (up to 18 electrons) More than 8 electrons shared Add valence shells if more than 8 valence electrons are around the central atom

1) Common Exceptions---H, He Only one electron pair needed to fill valence shell 2) Elements located AT or GREATER than 3 rd period. Exceed octet, EXPAND VALENCE SHELL, not electron deficient 3) Elements located WITHIN 2 nd Period. No surpassing octet, can be electron deficient **Octet rule applies to C, N, and O so applies to many molecules!!!

There is an error in each of these structures. What is it?

Only one Lewis Structure is correct. Identify it and state the problem (s) with the other structures.

Read pp Problems pp #53-54, 59-60