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In physics, 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, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from ...
When atomic mass is shown, it is usually the weighted average of naturally occurring isotopes; but if no isotopes occur naturally in significant quantities, the mass of the most stable isotope usually appears, often in parentheses. [8] In the standard periodic table, the elements are listed in order of increasing atomic number.
The abundance of the chemical elements is a measure of the occurrences of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by mass fraction (in commercial contexts often called weight fraction), by mole fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases), or by volume fraction.
Astatine is the rarest naturally occurring element. [j] The total amount of astatine in the Earth's crust (quoted mass 2.36 × 10 25 grams) [108] is estimated by some to be less than one gram at any given time. [8] Other sources estimate the amount of ephemeral astatine, present on earth at any given moment, to be up to one ounce [109] (about ...
This silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of both adjacent elements. The most common naturally occurring isotope is 99 Tc, in traces only.
BookRags, Periodic Table. World Book Encyclopedia, Exploring Earth. HyperPhysics, Georgia State University, Abundance of Elements in Earth's Crust. Eric Scerri, The Periodic Table, Its Story and Its Significance, Oxford University Press, 2007 "EarthRef.org Digital Archive (ERDA) -- Major Element Composition of the Core vs the Bulk Earth ...
Naturally occurring titanium is composed of five stable isotopes: 46 Ti, 47 Ti, 48 Ti, 49 Ti, and 50 Ti, with 48 Ti being the most abundant (73.8% natural abundance). At least 21 radioisotopes have been characterized, the most stable of which are 44 Ti with a half-life of 63 years; 45 Ti, 184.8 minutes; 51 Ti, 5.76 minutes; and 52 Ti, 1.7 minutes.
Selenium has seven naturally occurring isotopes. Five of these, 74 Se, 76 Se, 77 Se, 78 Se, 80 Se, are stable, with 80 Se being the most abundant (49.6% natural abundance). Also naturally occurring is the long-lived primordial radionuclide 82 Se, with a half-life of 8.76×10 19 years. [ 10 ]