protons are a kind of subatomic particle
group_of_subatomic_particles is group_of_things. subatomic_particle is natural_inanimate_thing. hydrogen_ion is proton. protons_and_neutrons is baryons. alpha_particle is subatomic_particle. subatomic_particle is microscopic_object. protons is component_of_atoms. proton is rocket. beta_particle is subatomic_particle. subatomic_particle is spatial_thing.