[DOC] [TLE] Thorium - Wikipedia [PAR] Of these, thorium (element 90) is the most stable, closely followed by uranium (
element 92): the isotope 232Th has a half-life of 14.05 billion years, about three 
times the ... are thus the most well-studied of all the radioactive elements. ... of 
thorium or its compounds contain traces of these daughters,... [DOC] [TLE] Decay chain - Wikipedia [PAR] In nuclear science, the decay chain refers to the radioactive decay of different 
discrete ... For example, uranium-238 is weakly radioactive, but pitchblende, a 
uranium ore, is 13 ... All the elements created more than 4.5 billion years ago are 
termed ... (half-life=700 million years) and thorium-232 (half-life=14 billion years). [DOC] [TLE] Thorium, Chemical Element - reaction, uses, elements, examples ... [PAR] One of its isotopes undergoes nuclear fission. Nuclear fission occurs when ... of 
thorium, thorium-232. Thorium-232 has a very long half life of 14 billion years. [DOC] [TLE] Copy of 8.01 Half-Life and Radioactive Decay by Kyle Wilmoth on ... [PAR] Mar 23, 2014 ... Thorium is a naturally occurring, radioactive chemical element. Chemical 
Properties ... is Thorium-232. It's half life is around 14 billion years. [DOC] [TLE] Geologic Time: Radiometric Time Scale [PAR] Jun 13, 2001 ... The discovery of the natural radioactive decay of uranium in 1896 by Henry 
Becquerel, ... loses particles from its nucleus to form an isotope of a new element 
(the daughter). ... Potassium-40, Argon-40, 1.25 billion years ... on the radioactive 
decay of the isotope carbon-14, which has a half-life of 5,730 years. [DOC] [TLE] How do we know the Age of the Earth? - USGS Geology in the Parks [PAR] Oct 31, 2014 ... The principal evidence for the antiquity of Earth and its cosmic ... Rocks 3.4-3.6 
billion years in age have been found in southern Africa, ... age of the universe is 
estimated to be around 14 billion years. ... By 1907 study of the decay products of 
uranium (lead and intermediate radioactive elements that decay... [DOC] [TLE] RADIOACTIVE AGE ESTIMATION METHODS - Do they prove the ... [PAR] The most common view is that Earth is approximately 4.5 billion years old. ... 
Various radioactive elements are involved, including Carbon-14, Uranium-238, 
Thorium-232, ... that all of the lead in a rock was produced by the decay of its 
uranium. [DOC] [TLE] HE 1523-0901 - SolStation.com [PAR] HE 1523-0901 lies very far away -- at least tens of thousands of light-years (ly) ... 
Because of its great distance from Earth, HE 1523-0901 is cannot be seen with 
the ... that from the abundance of the radioactive elements thorium and uranium (
in ... europium, and osmium) that the star was around 13.2 billion years old, 
which... [DOC] [TLE] Radiometric Dating [PAR] Absolute Dating.  any method of measuring the age of an event or object in 
years ... The process of the break down of radioactive isotopes into stable 
isotopes is ... o Uranium-238 decays to form Lead-206.  The unstable ... Each 
radioactive isotope has its own unique half-life. A half-life is the ... 14 billion years
. Uranium 235. [DOC] [TLE] Check and uncheck as needed to select sections to print. Then ... [PAR] Uranium and thorium, as well as three other radioactive elements, are used to 
date rocks. ... The rate at which the element decays is termed its half-life, which 
can be ... It would take another 14 billion years for half the remaining atoms to 
break... [DOC] [TLE] The creation of the universe - EAP Reading [PAR] However, when the existence of natural radioactive elements was ... Since the 
half-life periods of thorium and of common uranium are 14 billion and 4.5 billion 
... or about 6 billion years, to bring it down to its present rarity, if both isotopes 
were... [DOC] [TLE] Mineral Gallery: Radioactive Minerals [PAR] The radioactivity of an isotope is strongly dependent upon its half-life. ... of 700 
million years;

Question: For the radioactive element Thorium, it's about 14 billion years
Answer: Half-life