1.   At one level of understanding, electrons can be imagined as little points of electric charge that orbit the nuclei of atoms.

2.   But instead of two negatively charged electrons orbiting this nucleus, one of the electrons was replaced by a negatively charged antiproton.

3.   Electrons, which are in the lepton family, orbit the nuclei to complete the atomic structure.

4.   Fermions, named for the late Italian-American physicist Enrico Fermi, include the quarks that make up nuclear particles, and the electrons that orbit atomic nuclei.