The abundance of a chemical element measures how common the element is, or how much of the element there is. Abundance of the chemical elements - Abundance of elements in the Universe. Hydrogen is the most abundant element in the known Universe; helium is second. However, after this, the rank of abundance does not continue to correspond to the atomic number; oxygen has abundance rank 3, but atomic number 8. All others are orders of magnitude less common. Both helium-3 and helium-4 were produced in th ...

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• Abundance of the chemical elements - Abundance of elements in the Universe
• Abundance of the chemical elements - Abundance of elements in the Solar System
• Abundance of the chemical elements - Abundance of elements in Earth
• Abundance of the chemical elements - Abundance of elements in Earth's crust
• Abundance of the chemical elements - Ocean
• Abundance of the chemical elements - Atmosphere
• Abundance of the chemical elements - Organisms
• Abundance of the chemical elements - Human body

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All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus. Additionally, elements may exist in different isotopes, with each isotope of an element differing only in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are inherently unstable. That is, at some random point in time, an atom of such a nuclide will be transformed into a different nuclide by the process known as radioactive decay. This transformation is accomplished by the emission ...

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Radiometric dating, Radiometric dating - Types of radiometric dating, Radiometric dating - Fundamentals of radiometric dating, Radiometric dating - Limitation of techniques, Radiometric dating - Modern dating techniques, Radiometric dating - Short-range dating techniques, Radiometric dating - Dating with shortlived extinct radionuclides, Radiometric dating - Notes

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Radon is a carcinogenic gas. Radon is a radioactive material and must be handled with care at all times. It is hazardous to inhale this element since it emits alpha particles. Also, its solid decay products, and their respective products, tend to form a fine dust which can easily enter the airways and become permanently stuck in lung tissue, producing heavy localized exposure. Rooms where radium, actinium, or thorium are stored should be well-ventilated in order to prevent build-up in the air. The build-up of radon is a potential heal ...

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Radon, Radon - Notable characteristics, Radon - Applications, Radon - History, Radon - Occurrence, Radon - Compounds, Radon - Isotopes, Radon - Precautions, Radon - Radon therapy

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Research is currently picking up again for reactors that utilize molten salts for working fluids. Both the traditional molten salt reactor and the Very High Temperature Reactor (VHTR) have been picked as potential designs to be studied under the Generation Four Initiative (GEN-IV). A version of the VHTR currently being studied is the Liquid Salt Very High Temperature Reactor (LS-VHTR). It is essentially a standard VHTR design that uses liquid salt as a coolant instead of helium. It relies on "TRISO" fuel dispersed in graphite. The fue ...

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Molten salt reactor, Molten salt reactor - The aircraft reactor experiment, Molten salt reactor - The molten salt reactor experiment, Molten salt reactor - The final Oak Ridge National Laboratory molten salt reactor design 1976, Molten salt reactor - The liquid salt very high temperature reactor, Molten salt reactor - Fused salt selection, Molten salt reactor - Fused salt purification and reprocessing

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Ninety-one is a triangular number and a hexagonal number, one of the few such numbers to also be a centered hexagonal number, and it is also a centered nonagonal number and a centered cube number. It is the sum of the squares of the first six integers. It is also the lowest natural number which looks prime but isn't, because neither of its factors 7 and 13 have simple divisibility tests. It is the smallest positive integer expressible as a sum of two cubes in two different ways if negative roots are allowed: 91 = 63+(-5)3 = 43 ...

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91 number, 91 number - In mathematics, 91 number - In science, 91 number - In other fields

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Thorium is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium, and is about as common as lead. Soil commonly contains an average of around 6 parts per million (ppm) of thorium. Thorium occurs in several minerals, the most common being the rare earth-thorium-phosphate mineral, monazite, which contains up to about 12% thorium oxide. There are substantial deposits in several countries. Thorium-232 decays very slowly (its half-life is about three times the age of the earth) but other thorium ...

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Thorium, Thorium - Notable characteristics, Thorium - Applications, Thorium - History, Thorium - Occurrence, Thorium - Thorium as a nuclear fuel, Thorium - Isotopes, Thorium - Precautions, Thorium - Reference

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There's antimony, arsenic, aluminum, selenium, And hydrogen and oxygen and nitrogen and rhenium, And nickel, neodymium, neptunium, germanium, And iron, americium, ruthenium, uranium, Europium, zirconium, lutetium, vanadium, And lanthanum and osmium and astatine and radium, And gold and protactinium and indium and gallium, And iodine and thorium and thulium and thallium. There's yttrium, ytterbium, actinium, rubidium, And boron, gadolinium, niobium, iridium, And strontium and silicon and silver and samarium, And bismuth, bromine, l ...

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The Elements song, The Elements song - Lyrics, The Elements song - Periodic Table according to Lehrer

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Silvery in appearance, neptunium metal is fairly chemically reactive and is found in at least three structural modifications: alpha-neptunium, orthorhombic, density 20.25 Mg/m3, beta-neptunium (above 280 °C), tetragonal, density (313 °C) 19.36 Mg/m3, and gamma-neptunium (above 577 °C), cubic, density (600 °C) 18 Mg/m3. This element has four ionic oxidation states while in solution: Np+3 (pale purple), analogous to the rare earth ion PmSee also:

Neptunium, Neptunium - Notable characteristics, Neptunium - History, Neptunium - Occurrence, Neptunium - Isotopes, Neptunium - Weapons applications

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Scientists believe that the Earth formed from the same cloud of matter that formed the Sun. Abundance of the chemical elements - Abundance of elements in Earth's crust. The graphic below illustrates the relative abundance of the chemical elements in Earth's upper continental crust. Many of the elements shown in the graphic are classified into (partially overlapping) categories: rock-forming elements (major elements in green field and minor elements in light green field); ...

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Abundance of the chemical elements, Abundance of the chemical elements - Abundance of elements in the Universe, Abundance of the chemical elements - Abundance of elements in the Solar System, Abundance of the chemical elements - Abundance of elements in Earth, Abundance of the chemical elements - Abundance of elements in Earth's crust, Abundance of the chemical elements - Ocean, Abundance of the chemical elements - Atmosphere, Abundance of the chemical elements - Organisms, Abundance of the chemical elements - Human body

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On average, there is one atom of radon in 1 x 1021 molecules of air. Radon can be found in some spring waters and hot springs. The towns of Misasa, Japan, and Bad Kreuznach, Germany boast radium-rich springs which emit radon. Radon exhausts naturally from the ground, particularly in certain regions, especially but not only regions with granitic soils. Not all granitic regions are prone to high emissions of radon. Depending on how houses are built and ventilated, radon may accumulate in basements and dwellings. The European ...

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Radon, Radon - Notable characteristics, Radon - Applications, Radon - History, Radon - Occurrence, Radon - Compounds, Radon - Isotopes, Radon - Precautions, Radon - Radon therapy

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There are twenty known isotopes of radon. The most stable isotope is radon-222, which is a decay product (daughter product) of radium-226, has a half-life of 3.823 days and emits radioactive alpha particles. Radon-220 is a natural decay product of thorium and is called thoron. It has a half-life of 55.6 seconds and also emits alpha rays. Radon-219 is derived from actinium, is called actinon, is an alpha emitter an ...

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Radon, Radon - Notable characteristics, Radon - Applications, Radon - History, Radon - Occurrence, Radon - Compounds, Radon - Isotopes, Radon - Precautions, Radon - Radon therapy

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The Solar System was created from the remnants of previous stellar systems that went supernova, and is hence, relative to the rest of the universe, richer in heavier elements. Population I stars contain significant amounts of elements heavier than helium ("metals", in the terminology of astronomers). These heavy elements were produced by earlier generations of stars and spread by supernova explosions ...

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Abundance of the chemical elements, Abundance of the chemical elements - Abundance of elements in the Universe, Abundance of the chemical elements - Abundance of elements in the Solar System, Abundance of the chemical elements - Abundance of elements in Earth, Abundance of the chemical elements - Abundance of elements in Earth's crust, Abundance of the chemical elements - Ocean, Abundance of the chemical elements - Atmosphere, Abundance of the chemical elements - Organisms, Abundance of the chemical elements - Human body

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The types of fused salts that are chosen come from an optimization of salt characteristics. Fused fluorides are generally chosen over other salts because of the usefulness of the elements without isotope separation, better neutron economy and moderating efficiency, lower vapor pressure and better chemical stability. Chlorides have also been considered for molten salt reactors, but not nearly as much work has been done on reactor designs that utilize them. Additionally, whenever lithium fluoride is used as part of the salt composition, the lithium must be enriched to a very high purity (99. ...

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Molten salt reactor, Molten salt reactor - The aircraft reactor experiment, Molten salt reactor - The molten salt reactor experiment, Molten salt reactor - The final Oak Ridge National Laboratory molten salt reactor design 1976, Molten salt reactor - The liquid salt very high temperature reactor, Molten salt reactor - Fused salt selection, Molten salt reactor - Fused salt purification and reprocessing

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Hydrogen is the most abundant element in the known Universe; helium is second. However, after this, the rank of abundance does not continue to correspond to the atomic number; oxygen has abundance rank 3, but atomic number 8. All others are orders of magnitude less common. Both helium-3 and helium-4 were produced in the Big Bang. Additional helium is produced by the fusion of hydrogen inside stellar cores, via a process called the proton-proton chain. Hydrogen and helium are estimated to make up roughly 80% and 20% of all the m ...

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Abundance of the chemical elements, Abundance of the chemical elements - Abundance of elements in the Universe, Abundance of the chemical elements - Abundance of elements in the Solar System, Abundance of the chemical elements - Abundance of elements in Earth, Abundance of the chemical elements - Abundance of elements in Earth's crust, Abundance of the chemical elements - Ocean, Abundance of the chemical elements - Atmosphere, Abundance of the chemical elements - Organisms, Abundance of the chemical elements - Human body

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Radon (named for radium) was discovered in 1900 by Friedrich Ernst Dorn, who called it radium emanation. In 1908 William Ramsay and Robert Whytlaw-Gray, who named it niton (Latin nitens meaning "shining"; symbol Nt), isolated it, determined its density and that it was the heaviest known gas. It has been called radon since 1923. The danger of radon exposure in dwellings was discovered in 1984 by Stanley Watras, an employee at the Limerick nuclear power plant in Pennsylvania. Mr. Watras set off the radiation alarms on his ...

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Radon, Radon - Notable characteristics, Radon - Applications, Radon - History, Radon - Occurrence, Radon - Compounds, Radon - Isotopes, Radon - Precautions, Radon - Radon therapy

Read more here: » Radon: Encyclopedia II - Radon - History

Essentially chemically inert, but radioactive, radon is the heaviest noble gas and one of the heaviest gases at room temperature. (The heaviest is Uranium hexafluoride, UF6.) At standard temperature and pressure radon is a colorless gas but when it is cooled below its freezing point it has a brilliant phosphorescence which turns yellow as the temperature is lowered and orange-red at the temperature air liquefies. Natural radon concentrations in Earth's atmosphere are so low that natural waters in contact with the atmosphere ...

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Radon, Radon - Notable characteristics, Radon - Applications, Radon - History, Radon - Occurrence, Radon - Compounds, Radon - Isotopes, Radon - Precautions, Radon - Radon therapy

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Powdered thorium metal is often pyrophoric and should be handled carefully. The thorium decay chain ends with an isotope of lead (208-Pb), but passes through an isotope of radon (220-Rn) (also called "thoron")[2]. Radon gas is a radiation hazard. Good ventilation of areas where thorium is stored or handled is therefore essential. Exposure to thorium in the air can lead to increased risk of cancers of the lung, pancreas and blood. Exposure to thorium internally leads to increased risk of liver diseases. This element has no know ...

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Thorium, Thorium - Notable characteristics, Thorium - Applications, Thorium - History, Thorium - Occurrence, Thorium - Thorium as a nuclear fuel, Thorium - Isotopes, Thorium - Precautions, Thorium - Reference

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Naturally occurring thorium is composed of one isotope: 232-Th. twenty five radioisotopes have been characterized with the most {abundant and/or stable} being 232-Th with a half-life of 14.05 billion years, 230-Th with a half-life of 75,380 years, 229-Th with a half-life of 7340 years, and 228-Th with a half-life of 1.92 years. All of the remaining radioactive isotopes have half-lifes that are less than thirty days and the majority of these have half lifes that are less than ten minutes. This element also has one meta state. The isotopes of thorium range in atomic weight from 2 ...

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Thorium, Thorium - Notable characteristics, Thorium - Applications, Thorium - History, Thorium - Occurrence, Thorium - Thorium as a nuclear fuel, Thorium - Isotopes, Thorium - Precautions, Thorium - Reference

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19 neptunium radioisotopes have been characterized, with the most stable being Np-237 with a half-life of 2.14 million years, Np-236 with a half-life of 154,000 years, and Np-235 with a half-life of 396.1 days. All of the remaining radioactive isotopes have half-lifes that are less than 4.5 days, and the majority of these have half lifes that are less than 50 minutes. This element also has 4 meta states, with the most stable bein ...

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Neptunium, Neptunium - Notable characteristics, Neptunium - History, Neptunium - Occurrence, Neptunium - Isotopes, Neptunium - Weapons applications

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Radiometric dating can be performed on samples as small as a billionth of a gram using a mass spectrometer. The mass spectrometer was invented in the 1940s and began to be used in radiometric dating in the 1950s. The mass spectrometer operates by generating a beam of ionized atoms from the sample under test. The ions then travel through a magnetic field, which diverts them into different sampling sensors, known as "Faraday cups", depending on their mass and level of ionization. On impact in the cups, the ions set up a very weak current that can be measured to determine the rate of impacts a ...

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Radiometric dating, Radiometric dating - Types of radiometric dating, Radiometric dating - Fundamentals of radiometric dating, Radiometric dating - Limitation of techniques, Radiometric dating - Modern dating techniques, Radiometric dating - Short-range dating techniques, Radiometric dating - Dating with shortlived extinct radionuclides, Radiometric dating - Notes

Read more here: » Radiometric dating: Encyclopedia II - Radiometric dating - Modern dating techniques