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.
Captain Atom called on to join him on his quest and provide a way for him to reach Sorcerers' World. Captain Atom appears as one of the central characters in "", a maxi-series that takes place during the wider "Brightest Day" event. At the start of the series, Captain Atom is recruited as part of a massive group of superheroes tasked with hunting down the JLI's founder and Ted Kord's murderer, Maxwell Lord. During an encounter with Max at the Justice League's former New York headquarters, Captain Atom is rendered unconscious alongside Fire, Ice, and Booster Gold. The former Justice League members