[akwalker]

One of my A level Chemistry students asked me why, if fragmentation occurs in organic molecules, do you not get species forming from these fragments more massive than the parent ion.  I muttered something about bigger ions stability and the negative inductive effect, but, as usual, I don't really know what I'm going on about.  Anyone out there care to help a poor Chemistry teacher before Katie complains to the Head and has me sacked for incompetence?

[enahs]

How does a mass spec work? You fragment the ions, and you are in either positive mode or negative mode. That is, you are only sending either the positive ions or negative ions towards the detector. If you have a bunch of positive ions, are they likely to react with each other? Same thing for negative.