Decay products from a nucleus with spin may be distributed non-isotropically with respect to that spin direction, either because of an external influence such as an electromagnetic field, or because the nucleus was produced in a dynamic process that constrained the direction of its spin.Such a parent process could be a previous decay, or a nuclear reaction.), and the process produces at least one daughter nuclide.Alpha decay is one type of radioactive decay, in which an atomic nucleus emits an alpha particle, and thereby transforms (or "decays") into an atom with a mass number decreased by 4 and atomic number decreased by 2. A radioactive nucleus with zero spin can have no defined orientation, and hence emits the total momentum of its decay products isotropically (all directions and without bias). However, for a collection of atoms, the collection's expected decay rate is characterized in terms of their measured decay constants or half-lives. The half-lives of radioactive atoms have no known upper limit, spanning a time range of over 55 orders of magnitude, from nearly instantaneous to far longer than the age of the universe.
All isotopes of a given element have the same number of protons in each atom.In some cases radiation can be used to treat diseased organs, or tumours.Five Nobel Laureates have been closely involved with the use of radioactive tracers in medicine.Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. 1979, 1986 © Harper Collins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Cite This Source (ī'sə-tōp') One of two or more atoms that have the same atomic number (the same number of protons) but a different number of neutrons.Carbon 12, the most common form of carbon, has six protons and six neutrons, whereas carbon 14 has six protons and eight neutrons.