Search results
Results from the WOW.Com Content Network
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.
Several fluorescent molecules can be used simultaneously (given that they do not overlap, cf. FRET), whereas with radioactivity two isotopes can be used (tritium and a low energy isotope, e.g. 33 P due to different intensities) but require special equipment (a tritium screen and a regular phosphor-imaging screen, a specific dual channel ...
Avoid using the systematic element names in such contexts even when talking about history, because they are not supposed to be used once the element actually has a trivial name. For isotopes of undiscovered elements, either systematic names (e.g. 296 Uue) or atomic numbers (e.g. 296 119) are acceptable for the symbols, but only the systematic ...
Cosmogenic isotopes (or cosmogenic nuclides) are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ atom. These isotopes are produced within earth materials such as rocks or soil, in Earth's atmosphere , and in extraterrestrial items such as meteorites .
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example, carbon-13 with 6 protons and 7 neutrons. The nuclide concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the isotope concept (grouping all atoms of each element) emphasizes chemical over nuclear.
The decaying nucleus is called the parent radionuclide (or parent radioisotope), and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from a nuclear excited state, the decay is a nuclear transmutation resulting in a daughter containing a different number of protons or neutrons (or both).
They have shorter half-lives than primordial radionuclides. They arise in the decay chain of the primordial isotopes thorium-232, uranium-238, and uranium-235. Examples include the natural isotopes of polonium and radium. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to ...
All biologically active elements exist in a number of different isotopic forms, of which two or more are stable. For example, most carbon is present as 12 C, with approximately 1% being 13 C. The ratio of the two isotopes may be altered by biological and geophysical processes, and these differences can be utilized in a number of ways by ecologists.