Portal:Physics/Selected article/January 2008

In physics, the neutron is a baryon that consists of two down quarks and one up quark. Its strong force radiation is the primary force that holds atomic nuclei. It also has a mass of 1.008 664 915 (78) u (1.6749 × 10−27 kg (939.573 MeV/c²), but no electric charge. Neutrons additionally radiate beta decay and have a spin of ½. Neutrons are present in the majority of nuclei, however in a weighted majority they are not. The number of neutrons in a nucleus determines the isotope of the atom. For example, protium, or 1H, is an isotope of Hydrogen with no neutrons, while deuterium, or 2H, contains one. Neutrons were discovered in 1932 by Physicist James Chadwick two years after they were unexplainably detected by Physicist Walther Bothe.