natural isotopic abundance

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• Natural abundance — In chemistry, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average) of these isotopes is the atomic weight listed for the element in the… …   Wikipedia

• Natural nuclear fission reactor — Geological situation in Gabon leading to natural nuclear fission reactors 1. Nuclear reactor zones 2. Sandstone 3. Uranium ore layer 4. Granite A natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that …   Wikipedia

• Abundance of the chemical elements — Estimated proportions of matter, dark matter and dark energy in the universe. Only the fraction of the mass and energy in the universe labeled atoms is composed of chemical elements. The abundance of a chemical element measures how relatively… …   Wikipedia

• Isotopic labeling — (or isotopic labelling) is a technique for tracking the passage of a sample of substance through a system. The substance is labeled by including unusual isotopes in its chemical composition. If these unusual isotopes are later detected in a… …   Wikipedia

• Isotopic dilution — is a technique to increase the precision and accuracy of chemical analysis. First, a known amount of an isotope is added to the sample. For example, to determine the amount of lead in a sample, a known amount of Pb 204, one of the isotopes of… …   Wikipedia

• Nuclear magnetic resonance decoupling — (NMR decoupling for short) is a special method used in nuclear magnetic resonance (NMR) spectroscopy where a sample to be analyzed is irradiated at a certain frequency or frequency range to eliminate fully or partially the effect of coupling… …   Wikipedia

• Mononuclidic element — Not to be confused with the 26 monoisotopic elements defined as having only one stable nuclide. Set A is the 26 monoisotopic elements and B the 22 mononuclidic elements. The intersection consists of 19 elements that are both, but each set… …   Wikipedia

• isotope — isotopic /uy seuh top ik/, adj. isotopically, adv. /uy seuh tohp /, n. Chem. any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in… …   Universalium

• dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or …   Universalium

• mass spectrometry — or mass spectroscopy Analytic technique by which chemical substances are identified by sorting gaseous ions by mass using electric and magnetic fields. A mass spectrometer uses electrical means to detect the sorted ions, while a mass spectrograph …   Universalium

• Helium — otherusesHelium (He) is a colorless, odorless, tasteless, non toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2. Its boiling and melting points are the lowest among the… …   Wikipedia