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A schematic of the nucleus of an atom indicating β − radiation, the emission of a fast electron from the nucleus (the accompanying antineutrino is omitted). In the Rutherford model for the nucleus, a red sphere was a proton with positive charge, and a blue sphere was a proton tightly bound to an electron, with no net charge.
Sir James Chadwick (20 October 1891 – 24 July 1974) was an English physicist who received the Nobel Prize in Physics in 1935 for his discovery of the neutron.In 1941, he wrote the final draft of the MAUD Report, which inspired the U.S. government to begin serious atom bomb research efforts.
Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen nucleus. Neutrons are produced copiously in nuclear fission and fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes.
For example, in beta decay, a nitrogen-16 atom (7 protons, 9 neutrons) is converted to an oxygen-16 atom (8 protons, 8 neutrons) [31] within a few seconds of being created. In this decay a neutron in the nitrogen nucleus is converted by the weak interaction into a proton, an electron and an antineutrino. The element is transmuted to another ...
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment.
He found that nitrogen, and other light elements, ejected a proton, which he called a "hydrogen atom", when hit with α (alpha) particles. [22] In particular, he showed that particles ejected by alpha particles colliding with hydrogen have unit charge and 1/4 the momentum of alpha particles.
Owing to the rate of absorption of neutrons by the hydrogen in water, it was unlikely that a self-sustaining reaction could be achieved with natural uranium and water as a neutron moderator. Fermi suggested, based on his work with neutrons, that the reaction could be achieved with uranium oxide blocks and graphite as a moderator instead of ...
The prevailing model of atomic structure before Rutherford's experiments was devised by J. J. Thomson. [2]: 123 Thomson had discovered the electron through his work on cathode rays [3] and proposed that they existed within atoms, and an electric current is electrons hopping from one atom to an adjacent one in a series.