sumo#atomic_nucleus  the core of the atom; it is composed of protons and neutrons
  supertype:  sumo#subatomic_particle__subatomicparticle  the class of elemental_substances that are smaller than atoms and compose atoms
  part:  sumo#proton  components of the atomic_nucleus; they have a positive charge
  part:  sumo#neutron  components of the atomic_nucleus; they have no charge

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