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For example element 92, uranium, has an isotope with 144 neutrons (236 U) and it decays into an isotope of element 90, thorium, with 142 neutrons (232 Th). The daughter isotope may be stable or it may itself decay to form another daughter isotope. 232 Th does this when it decays into radium-228.
226 Ra is the most stable isotope of radium and is the last isotope in the (4 n + 2) decay chain of uranium-238 with a half-life of over a millennium; it makes up almost all of natural radium. Its immediate decay product is the dense radioactive noble gas radon (specifically the isotope 222 Rn ), which is responsible for much of the danger of ...
The decay-chain of uranium-238, which contains radium-226 as an intermediate decay product. 226 Ra occurs in the decay chain of uranium-238 (238 U), which is the most common naturally occurring isotope of uranium. It undergoes alpha decay to radon-222, which is also radioactive; the decay chain ultimately terminates at lead-206.
Most natural transmutation on the Earth today is mediated by cosmic rays (such as production of carbon-14) and by the radioactive decay of radioactive primordial nuclides left over from the initial formation of the Solar System (such as potassium-40, uranium and thorium), plus the radioactive decay of products of these nuclides (radium, radon ...
The decay chain of 238 U is commonly called the "radium series" (sometimes "uranium series"). Beginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium.
The decay chain of uranium-238, known as the uranium series or radium series, of which polonium-210 is a member Schematic of the final steps of the s-process.The red path represents the sequence of neutron captures; blue and cyan arrows represent beta decay, and the green arrow represents the alpha decay of 210 Po.
Uranium-236 occurs in spent nuclear fuel when neutron capture on 235 U does not induce fission, or as a decay product of plutonium-240. Uranium-236 is not fertile, as three more neutron captures are required to produce fissile 239 Pu, and is not itself fissile; as such, it is considered long-lived radioactive waste. [115]
Radon-222 (222 Rn, Rn-222, historically radium emanation or radon) is the most stable isotope of radon, with a half-life of approximately 3.8 days. It is transient in the decay chain of primordial uranium-238 and is the immediate decay product of radium-226.