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Commercial rubidium clocks are less accurate than caesium atomic clocks, which serve as primary frequency standards, so a rubidium clock is usually used as a secondary frequency standard. Commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6.8 GHz (6 834 682 610.904 Hz).
The dates indicate the true age of the minerals only if the rocks have not been subsequently altered. See rubidium–strontium dating for a more detailed discussion. Other than 87 Rb, the longest-lived radioisotopes are 83 Rb with a half-life of 86.2 days, 84 Rb with a half-life of 33.1 days, and 86 Rb with a half-life of 18.642 days. All other ...
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, a.k.a. phosphoric acid H 3 PO 4. The phosphate or orthophosphate ion [PO 4] 3− is derived from phosphoric acid by the removal of three protons H +.
Xenotime, a REE phosphate, is the main HREE ore containing as much as 60% yttrium as yttrium phosphate (YPO 4). [56] This applies to xenotime-(Y). [ 61 ] [ 64 ] [ 60 ] The largest mine is the Bayan Obo deposit in China, making China the largest exporter for HREE since the closure of the Mountain Pass mine in the 1990s.
Uranium is a naturally occurring element found in low levels in all rock, soil, and water. It is the highest-numbered element found naturally in significant quantities on Earth and is almost always found combined with other elements. [ 12 ]
The cadmium cut-off is about 0.5 eV, and neutrons below that level are deemed slow neutrons, distinct from intermediate and fast neutrons. [16] Cadmium is created via the s-process in low- to medium-mass stars with masses of 0.6 to 10 solar masses, over thousands of years.
Lanthanum, like the other lanthanides, is known to affect human metabolism, lowering cholesterol levels, blood pressure, appetite, and risk of blood coagulation. When injected into the brain, it acts as a painkiller, similarly to morphine and other opiates, though the mechanism behind this is still unknown. [ 80 ]
4, phosphate Zn 3 (PO 4) 2, molybdate ZnMoO 4, cyanide Zn(CN) 2, arsenite Zn(AsO 2) 2, arsenate Zn(AsO 4) 2 ·8H 2 O and the chromate ZnCrO 4 (one of the few colored zinc compounds) are a few examples of other common inorganic compounds of zinc. [69] [70] Organozinc compounds are those that contain zinc–carbon covalent bonds. Diethylzinc ((C ...