## Can there be molecular structures according to QM?

In molecular orbital theory, only the electrons are considered and from that we draw conclusions about molecular shape and such. I was thinking just now, what about the nuclei?

If we apply QM to the nuclei as well, wouldn't that mean that we can't know where the atoms are? or is the probability density very concentrated due to the relative size of the atom so that the location is more or less well defined?

For if the location of the nuclei isn't well defined, then how can we be certain of the molecular shape?