A hydrogen nucleus consists of a single proton.
A 2-hydrogen (deuterium) nucleus consists of a proton and a neutron.
A tritium nucleus consists of a proton and two neutrons.
This makes me wonder how an atomic nucleus made of a proton and a "minus one neutron" would look like, and the closest thing to a "minus one neutron" I can imagine is an antineutron.
What happens if we combine a proton and an antineutron? Are things like this even possible?
If such a thing is an atomic nucleus, can we add an electron and get an atom?
Edit: in the comments below, I also asked this more specific question (I suppose it's useful to also mention it here in order not to create a complete chaos):
If the proton and antineutron annihilate, is it still possible that the thing they annihilate to remains somehow stable enough to behave like an atomic nucleus?
Best Answer
In addition to dmckee's answer this link summarizes the experiments of antiprotons catching protons and neutrons, creating temporary nuclei.
It is the symmetric state to the one in the question : an anti-proton-neutron nucleus that lasts for a bit (fig 5.7). Anti-protons can be made in abundance and controlled experimentally because they are charged, anti-neutrons do not give easy handles.