Suppose you were to try to create a proton-antiproton pair by annihilation of a very high energy photon. The proton and the anti-proton have the same masses, but opposite charges. What energy photon would be required?

Elementary particles, also known as fundamental particles, are subatomic particles that are not made up of other particles. They are smaller than an atom and do not appear to be made up of a combination of more basic things. 
The Standard Model recognizes 17 distinct particles, including 12 fermions and five bosons.