Atom bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton. Neutrons have no electrical charge and have a free mass of 1,839 times the mass of the electron, or , the heaviest of the three constituent particles, but it can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions—on the order of —although the 'surface' of these particles is not sharply defined. The neutron was discovered in 1932 by the English physicist James Chadwick.
Mister Atom Mister Atom Mister Atom is a fictional comic book supervillain, a radioactive robot who is regularly seen as an enemy of Captain Marvel. Mister Atom first appeared in "Captain Marvel Adventures" #78 and was created by Otto Binder and C. C. Beck. Mister Atom was created by Dr. Charles Langley in a story in "Captain Marvel Adventures" #78. His body was constructed first, and then Langley charged the robot with radioactive energy. The spark that gave the robot life also ended the life of his creator. Super-charged with a nuclear reactor and armed with a deadly mind, Mister Atom went