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Gold is currently considered the heaviest monoisotopic element. Bismuth formerly held that distinction until alpha-decay of the 209 Bi isotope was observed. All isotopes of gold are either radioactive or, in the case of 197 Au, observationally stable, meaning that 197 Au is predicted to be radioactive but no actual decay has been observed. [4]
Naturally occurring platinum (78 Pt) consists of five stable isotopes (192 Pt, 194 Pt, 195 Pt, 196 Pt, 198 Pt) and one very long-lived (half-life 4.83×10 11 years) radioisotope (190 Pt). There are also 34 known synthetic radioisotopes , the longest-lived of which is 193 Pt with a half-life of 50 years.
Platinum also has 38 synthetic isotopes ranging in atomic mass from 165 to 208, making the total number of known isotopes 44. The least stable of these are 165 Pt and 166 Pt, with half-lives of 260 μs, whereas the most stable is 193 Pt with a half-life of 50 years. Most platinum isotopes decay by some combination of beta decay and alpha decay ...
For isotopes with atomic mass unit values less than that of the most abundant stable isotope, 106 Pd, the primary decay mode is electron capture with the primary decay product being rhodium. The primary mode of decay for those isotopes of Pd with atomic mass greater than 106 is beta decay with the primary product of this decay being silver. [14]
Atomic numbers are sometimes capped at 92 . [20] Definitions based on atomic number have been criticised for including metals with low densities. For example, rubidium in group (column) 1 of the periodic table has an atomic number of 37 but a density of only 1.532 g/cm 3, which is below the threshold figure used by other authors. [21]
Stable even–even nuclides number as many as three isobars for some mass numbers, and up to seven isotopes for some atomic numbers. Conversely, of the 251 known stable nuclides, only five have both an odd number of protons and odd number of neutrons: hydrogen-2 ( deuterium ), lithium-6 , boron-10 , nitrogen-14 , and tantalum-180m .
The U.S. Supreme Court rules that bump stocks are not the same as machine guns and cannot be outlawed. Supreme Court strikes down ban on rapid-fire bump stocks like those used in Las Vegas mass ...
Although mercury is an extremely rare element in the Earth's crust, [68] because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be highly concentrated considering the element's abundance in ordinary rock. The richest mercury ores contain up to 2.5% mercury by mass, and even ...