. "A simple hydrogen atom is composed of a single proton and a single electron orbiting it in an s-shell. Isotopes of hydrogen, deuterium and tritium, have an additional (1) neutron and 2 neutrons, respectively."@en . . . "What is the structure of hydrogen"@en . "A simple hydrogen atom is composed of a single proton and a single electron orbiting it in an s-shell. Isotopes of hydrogen, deuterium and tritium, have an additional (1) neutron and 2 neutrons, respectively."@en .