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Francium is one of the most unstable of the naturally occurring elements: its longest-lived isotope, francium-223, has a half-life of only 22 minutes. The only comparable element is astatine , whose most stable natural isotope, astatine-219 (the alpha daughter of francium-223), has a half-life of 56 seconds, although synthetic astatine-210 is ...
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.
Loss of potency requires periodic replacement of the source in radiotherapy and is one reason why cobalt machines have been largely replaced by linear accelerators in modern radiation therapy. [175] Cobalt-57 (Co-57 or 57 Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for vitamin B 12 uptake, and for the ...
Calcium hydride is the chemical compound with the formula CaH 2, an alkaline earth hydride. This grey powder (white if pure, which is rare) reacts vigorously with water, liberating hydrogen gas. CaH 2 is thus used as a drying agent, i.e. a desiccant .
"periodic table" will have an interactive 3d element from the periodic table, clicking the "explore elements" button will navigate to artsexperiments.withgoogle.com [102] "play dreidel" or "dreidel" will spin a dreidel, landing on one of four letters of the Hebrew alphabet: נ , ג , ה or ש .
Mesons named with the letter "f" are scalar mesons (as opposed to a pseudo-scalar meson), and mesons named with the letter "a" are axial-vector mesons (as opposed to an ordinary vector meson) a.k.a. an isoscalar vector meson, while the letters "b" and "h" refer to axial-vector mesons with positive parity, negative C-parity, and quantum numbers I G of 1 + and 0 − respectively.
Sphalerite is a sulfide mineral with the chemical formula (Zn, Fe)S. [5] It is the most important ore of zinc.Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Valley type, and volcanogenic massive sulfide deposits.
The table below lists the known reasons for core collapse in massive stars, the types of stars in which they occur, their associated supernova type, and the remnant produced. The metallicity is the proportion of elements other than hydrogen or helium, as compared to the Sun. The initial mass is the mass of the star prior to the supernova event ...