nucleon       
noun [ C ]  physics specialized uk/ˈnjuː.kli.ɒn/ us/ˈnuː.kli.ɑːn/
 核子,质子或中子
a proton (= an extremely small piece of matter with a positive electrical charge) or a neutron (= an extremely small piece of matter with no electrical charge) in an atom
  The separate nucleons have more mass than the nucleus itself. 原子核内的核子分离后,总质量比原子核更大。 
 See also: internucleon
 - More examples
 - The nucleus is made up of particles called nucleons.
 - The nucleons are bound tightly together by the strong nuclear force.
 - If a nucleus is formed from separate nucleons, energy is released.
 - If two light nuclei fuse, the final binding energy per nucleon will be greater than the original value.