Thank you all for explaining, I'm glad it was my pedantic lack of ability to get over the description and think of the chemistry that was the problem. Of course the positive charge would not be localised just on the hydrogen, it is not really just a proton and so it will have some electron density.
Peter On 2 February 2015 at 13:08, Peter Moody <[email protected]> wrote: > Dear BB > > > I have (again) realised how limited by understanding of our subject is. > > > In Nature’s online site > http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14110.html?WT.ec_id=NATURE-20150129 > there is a paper describing an X-ray structure determined with sub-atomic > data (nice!). The figures show density for H+ as well as H-. In my > simple way I had assumed that any X-ray scattering from the nucleus was > negligible, and that the electrons are responsible for this. I would expect > a proton (i.e. H+) alone to be invisible to X-rays, and certainly not to > look similar to a hydride (with two electrons in (electron density) maps. > What have I missed? Could someone please explain, or point me to a > suitable reference? > > > Best wishes, Peter > > (please use [email protected] to reply directly) > > http://www2.le.ac.uk/departments/biochemistry/staff/moody > >
