Energy absorption by protons/neutrons in and out of nuclei As I'm studying quantum mechanics, I find a lot of discussion about electron absorption/emission of photons, energy levels, etc. My questions are 


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*When, say, a hydrogen atom absorbs energy, is it only able to be absorbed by the electron?  Could, say, the proton absorb energy and change the momentum of the atom (assuming it's a free atom)?

*Does a free proton behave in the same way as an electron (wave function, uncertainty in $x p \geq \hbar/2$)?

*Does a bound proton in a hydrogen atom have uncertainty in its position as well?

*How about the quarks that make up a proton?

 A: Yes, a hydrogen atom could absorb energy and change momentum.  However, the momentum of the atom is largely dictated by the nucleus (the proton), and the nucleus is mostly shielded from interactions with photons by the electron.
A proton is not a fundamental particle like an electron is, so it doesn't behave exactly the same, but to a good approximation yes a proton just like everything else (including you and also the entire earth) has a wave function that obeys the uncertainty principle.  Remember though that since protons are much more massive than electrons, their uncertainty in position is typically much less.
Yes, a bound proton also has uncertainty in its position, we just usually define the origin of the atom to be the proton because we often don't care about the overall movement of the atom, for instance when solving for the electron orbitals.
Quarks are fundamental particles just like electrons.  They also obey the uncertainty principle because everything does.  The behavior of quarks is much more complicated though.  For instance, it is impossible to observe a free quark because the amount of energy it would take to break it free from a bound state is so great that it would create another quark to bind to.
