Lecture 12: Exceptions to Octet Rule, Formal Charge, Resonance

What are exceptions to the octet rule?

1. The octet rule cannot be satisfied whose total number of valence electrons is an odd number

2. There are also molecules in which an atom has fewer, or more, than a complete octet in the valence electrons

Which elements are strict adherents to the octet rule?

C, O, N, and F

Which elements take an “Expanded Octet”

Any atom with more than 8 electrons, period 2 and below

Which elements qualify for the “Incomplete Octet”

Groups 1, 2, and 13

Formal Charge

The charge calculated for an atom in a Lewis structure on the basis of an equal sharing of bonded electron pairs

How to calculate formal charge

Formal charge = group number in periodic table - number of bonds - number of unshared electrons

What is the strongest type of bond?

A triple bond

What types of bonds have the most energy?

Triple bonds