Lonesome in Massachussets: How about a neutron and an anti-proton? Do you happen to know of a table of subatomic particles that shows which particles and anti-particles will annihilate if they come into contact?
Good question, Mind-numbed Robot. I had never considered it before.
Google antimatter and look in wikipedia. Every particle is believed to have an antiparticle.
“How about a neutron and an anti-proton?”
By themselves, the neutron doesn’t directly interact with the anti-proton, I think; but the neutron can lose a bit of energy (e=mc^2 and all that) and decay into a proton. They aren’t static marbles, subatomic particles are changing state all the time. There’s a full menagerie of them (https://secure.wikimedia.org/wikipedia/en/wiki/List_of_particles) and their relationships and interactions are quite interesting.