Question

I have to build a model of a molecule and I was wondering how to determine its bond lenghts.
(It has C-H, C-O, C=O, C-N, C-C & C=C bonds.)
Also, will the lengths of all of one type of bond be the same throughout the molecule? Er...for example, if I found the length of a C-H bond, would every C-H bond be the same length in this molecule?

Answer 1

Bond lengths are not always the same for a particular bond. Most references give average bond lengths. Here is a good site that gives averages plus some specific lengths depending upon the environment.http://ww1.iucr.org/comm/cteach/pamphlets/15/node6.html

Answer 2

Bond angles are more important in building molecular models than bond lengths. You can get approximate bond lengths by looking up the covalent radius of both elements linked and add them up. Double and triple bonds are shorter than single bonds. Some of the bonds you need are here:
http://www.science.uwaterloo.ca/~cchieh/cact/c120/bondel.html