Search results
Results from the WOW.Com Content Network
Half-life (symbol t ½) is the time required for a quantity (of substance) to reduce to half of its initial value.The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10 −19 and 10 −10 seconds. [1]
The half-life, t 1/2, is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value. The decay constant , λ " lambda ", the reciprocal of the mean lifetime (in s −1 ), sometimes referred to as simply decay rate .
At least 3,300 nuclides have been experimentally characterized [1] (see List of radioactive nuclides by half-life for the nuclides with decay half-lives less than one hour). A nuclide is defined conventionally as an experimentally examined bound collection of protons and neutrons that either is stable or has an observed decay mode .
Radioactive nonprimordial, but naturally occurring on Earth. 61 347 Carbon-14 (and other isotopes generated by cosmic rays) and daughters of radioactive primordial elements, such as radium, polonium, etc. 41 of these have a half life of greater than one hour. Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful radiotracers. 662 989
Half-life T 1/2 is defined as the length of time for half of a given quantity of radioactive atoms to undergo radioactive decay: = /. Taking the natural logarithm of both sides, the half-life is given by / = .
Three other radon isotopes have a half-life of over an hour: 211 Rn (about 15 hours), 210 Rn (2.4 hours) and 224 Rn (about 1.8 hours). However, none of these three occur naturally. 220 Rn, also called thoron, is a natural decay product of the most stable thorium isotope (232 Th). It has a half-life of 55.6 seconds and also emits alpha radiation.
Iodine-131 (131 I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. [3] It has a radioactive decay half-life of about eight days.