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[g] Lead has a magic number of protons (82), for which the nuclear shell model accurately predicts an especially stable nucleus. [39] Lead-208 has 126 neutrons, another magic number, which may explain why lead-208 is extraordinarily stable. [39] With its high atomic number, lead is the heaviest element whose natural isotopes are regarded as ...
The Keulegan–Carpenter number is important for the computation of the wave forces on offshore platforms. In fluid dynamics , the Keulegan–Carpenter number , also called the period number , is a dimensionless quantity describing the relative importance of the drag forces over inertia forces for bluff objects in an oscillatory fluid flow .
Period 5 has the same number of elements as period 4 and follows the same general structure but with one more post transition metal and one fewer nonmetal. Of the three heaviest elements with biological roles, two (molybdenum and iodine) are in this period; tungsten, in period 6, is heavier, along with several of the early lanthanides.
Lead (82 Pb) has four observationally stable isotopes: 204 Pb, 206 Pb, 207 Pb, 208 Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide.The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay chains: the uranium series (or radium series), the actinium series, and the thorium series, respectively; a fourth decay chain, the neptunium series ...
For instance, the radii generally decrease rightward along each period (row) of the table, from the alkali metals to the noble gases; and increase down each group (column). The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period.
The stability of nuclei decreases greatly with the increase in atomic number after curium, element 96, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day. No elements with atomic numbers above 82 (after lead) have stable isotopes. [107]
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Rutherford applied the principle of a radioactive element's half-life in studies of age determination of rocks by measuring the decay period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for the exponential decay equation.