Lecture #13
  CURMUDGEON GENERAL'S WARNING. These "slides" represent highlights from lecture and are neither complete nor meant to replace lecture. It is advised not to use these as a reliable means to replace missed lecture material. Do so at risk to healthy academic performance in 09-105.
Lecture Outline Molecular Structure


Equivalent preferred contributors

Bond order

Line Structures

Reaction Heats

A sample question about Lewis structures and bond orders for some oxide ions of astatine (Z=85).
Introducing the shorthand symbolism of "line structures". This is not in the text.  
 Line structures are a useful and very common way of presenting Lewis structures. They are essentially geometric abbreviations.  
 Here are two illustrations of line structures that look similar, but aren't quite the same.  
An application: We'll diverge slightly and discuss bond energies and one way in which they can be applied, the energy released (reaction heat) in the combustion of octane. Here we get the balanced equation for the complete combustion reaction. (Reaction heats are not covered in the text.)  
In order to take a look at the energy change involved, we look at the "structures" of the various reaction components.  
We can then calculate the net energy change when electrons re-arrange their "allegiance", that is, some bonds break and others form. The various bond energies can be obtained from data bases (tables in the text, for example)