Iridium

"Iridium ( /ɨˈrɪdiəm/ i-rid-ee-əm) is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element (after osmium) and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable."

"Iridium was discovered in 1803 among insoluble impurities in natural platinum. Smithson Tennant, the primary discoverer, named the iridium for the goddess Iris, personification of the rainbow, because of the striking and diverse colors of its salts. Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only three tonnes. ¹⁹¹Ir and ¹⁹³Ir are the only two naturally occurring isotopes of iridium as well as the only stable isotopes; the latter is the more abundant of the two."

"The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in industrial catalysis, and in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, as in high-end spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators."

Ultraviolet Radiation

"Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, that is, in the range 10 nm to 400 nm, corresponding to photon energies from 3 eV to 124 eV. It is so-named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet. These frequencies are invisible to humans, but visible to a number of insects and birds."

"UV light is found in sunlight (where it constitutes about 10% of the energy in vacuum) and is emitted by electric arcs and specialized lights such as black lights. It can cause chemical reactions, and causes many substances to glow or fluoresce. Most ultraviolet is classified as non-ionizing radiation. The higher energies of the ultraviolet spectrum from wavelengths about 10 nm to 120 nm ('extreme' ultraviolet) are ionizing, but this type of ultraviolet in sunlight is blocked by normal dioxygen in air, and does not reach the ground.^[1] However, the entire spectrum of ultraviolet radiation has some of the biological features of ionizing radiation, in doing far more damage to many molecules in biological systems than is accounted for by simple heating effects (an example issunburn). These properties derive from the ultraviolet photon's power to alter chemical bonds in molecules, even without having enough energy to ionize atoms."

Neodymium

"Neodymium ( /ˌniːɵˈdɪmiəm/ nee-o-dim-ee-əm) is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal thattarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. It is present in significant quantities in the ore minerals monazite and bastnäsite. Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Although neodymium is classed as a "rare earth", it is no rarer than cobalt, nickel, and copper ore, and is widely distributed in the Earth's crust.^[2] Most of the world's neodymium is mined in China."

"Neodymium compounds were first commercially used as glass dyes in 1927, and they remain a popular additive in glasses. The color of neodymium compounds—due to the Nd(III) ion—is often a reddish-purple but it changes with the type of lighting, due to fluorescent effects. Some neodymium-doped glasses are also used in lasers that emit infrared light with wavelengths between 1047 and 1062 nanometers. These have been used in extremely high power applications, such as experiments in inertial confinement fusion."

"Neodymium is also used with various other substrate crystals, such as yttrium aluminum garnet in the Nd:YAG laser. This laser usually emitsinfrared waves at a wavelength of about 1064 nanometers. The Nd:YAG laser is one of the most commonly used solid-state lasers."

Indium

"Indium ( /ˈɪndiəm/ in-dee-əm) is a chemical element with symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows intermediate properties between these two. Indium was discovered in 1863 and named for the indigo blue line in its spectrum that was the first indication of its existence in zinc ores, as a new and unknown element. The metal was first isolated in the following year. Zinc ores continue to be the primary source of indium, where it is found in compound form. Very rarely the element can be found as grains of native (free) metal, but these are not of commercial importance."

"Indium's current primary application is to form transparent electrodes from indium tin oxide (ITO) in liquid crystal displays and touchscreens, and this use largely determines its global mining production. It is widely used in thin-films to form lubricated layers (during World War II it was widely used to coat bearings in high-performance aircraft). It is also used for making particularly low melting point alloys, and is a component in some lead-free solders."

"Indium is not known to be used by any organism. In a similar way to aluminium salts, indium(III) ions can be toxic to the kidney when given by injection, but oral indium compounds do not have the chronic toxicity of salts of heavy metals, probably due to poor absorption in basic conditions. Radioactive indium-111 (in very small amounts on a chemical basis) is used in nuclear medicine tests, as a radiotracer to follow the movement of labeled proteins and white blood cells in the body."

Fermion

"In particle physics, a fermion (a name coined by Paul Dirac^[1] from the surname of Enrico Fermi) is any particle characterized by Fermi–Dirac statistics and following the Pauli exclusion principle; fermions include all quarks and leptons, as well as any composite particle made of an odd number of these, such as all baryons and many atoms and nuclei. Fermions contrast with bosons which obey Bose–Einstein statistics."

"A fermion can be an elementary particle, such as the electron; or it can be a composite particle, such as the proton. The spin-statistics theorem holds that, in any reasonable relativistic quantum field theory, particles with integer spin are bosons, while particles with half-integer spin are fermions."

"In contrast to bosons, only one fermion can occupy a particular quantum state at any given time. If multiple fermions have the same spatial probability distribution, then at least one property of each fermion, such as its spin, must be different. Fermions are usually associated with matter, whereas bosons are generally force carrier particles; although in the current state of particle physics the distinction between the two concepts is unclear."

"The Standard Model recognizes two types of elementary fermions: quarks and leptons. In all, the model distinguishes 24 different fermions: 6 quarks and 6 leptons, each with a corresponding anti-particle."

Ytterbium

"Ytterbium ( /ɨˈtɜrbiəm/ i-tur-bee-əm) is a chemical element with symbol Yb and atomic number 70. It is the fourteenth and penultimate element in the lanthanide series, or last element in the f-block, which is the basis of the relative stability of the +2 oxidation state. However, like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other compounds. In an aqueous solution, like compounds of other late lanthanides, soluble ytterbium compounds form complexes with nine water molecules."

"In 1878, the Swiss chemist Jean Charles Galissard de Marignac separated in the rare earth of "erbia" another independent component, which he called "ytterbia", for Ytterby, the Swedish village near where he found the new component of erbium. He suspected that ytterbia was a compound of a new element that he called "ytterbium" (note that in total four elements were named after the village, the others being yttrium, terbium and erbium). In 1907, the new earth "lutecia" was separated from ytterbia, from which the element "lutecium" (now lutetium) was extracted. A relatively pure sample of the metal was obtained only in 1953. In present, ytterbium is mainly used as a dopant of stainless steel or active laser media, and less often as a gamma ray source."

"Natural ytterbium is a mixture of seven stable isotopes, which altogether are present at concentrations of 3 ppm. This element is mined in China, the United States, Brazil, and India in form of the minerals monazite, euxenite, and xenotime. The ytterbium concentration is low, because the element is found among many other rare earth elements; moreover, it is among the least abundant ones. Once extracted and prepared, ytterbium is somewhat hazardous as an eye and skin irritant. The metal is a fire and explosion hazard."

Californium

"Californium is a radioactive metallic chemical element with the symbol Cf and atomic number 98. The element was first made at the University of California, Berkeley in 1950 by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixthtransuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The element was named after California and the University of California. It is the heaviest element to occur naturally on Earth; heavier elements can only be produced by synthesis."

"Two crystalline forms exist for californium under normal pressure: one above 900 °C and one below 900 °C. A third form exists at high pressure. Californium slowly tarnishes in air at room temperature. Compounds of californium are dominated by a chemical form of the element, designated californium(III), that can participate in three chemical bonds. The most stable of californium's twenty known isotopes is californium-251, which has a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust.^[a] Californium-252, with a half-life of about 2.64 years, is the most common isotope used and is produced at the Oak Ridge National Laboratory in the United States and the Research Institute of Atomic Reactors in Russia."

Preon

"In particle physics, preons are postulated "point-like" particles, conceived to be subcomponents of quarks and leptons.^[1] The word was coined by Jogesh Pati and Abdus Salam in 1974. Interest in preon models peaked in the 1980s but has slowed as the Standard Model of particle physics continues to describe the physics mostly successfully, and no direct experimental evidence for lepton and quark compositeness has been found, although in the hadronic sector there are some intriguing open questions and some effects considered as anomalies within the Standard Model. For example, four very important open questions are the proton spin puzzle, the EMC effect, the distributions of electric charges of the nucleons found by Hofstadter in 1956, and the ad hoc CKM matrix elements."

"A number of physicists have attempted to develop a theory of "pre-quarks" (from which the name preon derives) in an effort to justify theoretically the many parts of the Standard Model that are known only through experimental data."

"Other names which have been used for these proposed fundamental particles (or particles intermediate between the most fundamental particles and those observed in the Standard Model) include prequarks, subquarks, maons,^[3] alphons, quinks, Rishons, tweedles, helons, haplons, and Y-particles.,^[4] primons.^[5] Preon is the leading name in the physics community."

Gadolinium

"Gadolinium ( /ˌɡædɵˈlɪniəm/ gad-o-lin-ee-əm) is a chemical element with symbol Gd and atomic number 64. It is a silvery-white, malleable andductile rare-earth metal. It is found in nature only in combined (salt) form. Gadolinium was first detected spectroscopically in 1880 by de Marignacwho separated its oxide and is credited with its discovery. It is named for gadolinite, one of the minerals in which it was found, in turn named for chemist Johan Gadolin. The metal was isolated by Lecoq de Boisbaudran in 1886."

"Gadolinium metal possesses unusual metallurgic properties, to the extent that as little as 1% gadolinium can significantly improve the workability and resistance to high temperature oxidation of iron, chromium, and related alloys. Gadolinium as a metal or salt has exceptionally high absorption of neutrons and therefore is used for shielding in neutron radiography and in nuclear reactors. Like most rare earths, gadolinium formstrivalent ions which have fluorescent properties. Gd (III) salts have therefore been used as green phosphors in various applications."

Astatine

"Astatine (/ˈæstətiːn/ as-tə-teen or /ˈæstətɪn/ as-tə-tin) is a radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth only as the result of the radioactive decay of certain heavier elements. All of its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours. Accordingly, much less is known about astatine than most other elements. The observed properties are consistent with it being a heavier analog of iodine; many other properties have been estimated based on this resemblance."

"Elemental astatine has never been viewed, because a mass large enough to be seen (by the naked human eye) would be immediately vaporized by the heat generated by its own radioactivity. Astatine may be dark, or it may have a metallic appearance and be a semiconductor, or it may even be a metal. It is likely to have a much higher melting point than does iodine, on par with those of bismuth and polonium. Chemically, astatine behaves more or less as a halogen, being expected to form ionic astatides with alkali or alkaline earth metals; it is known to form covalent compounds with nonmetals, including other halogens. It does, however, also have a notable cationic chemistry that distinguishes it from the lighter halogens. The second longest-lived isotope of astatine, astatine-211, is the only one currently having any commercial application, being employed in medicine to diagnose and treat some diseases via its emission of alpha particles (helium-4 nuclei). Only extremely small quantities are used, however, due to its intense radioactivity."