Yttrium

Yttrium is a chemical element with symbol "Y" and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is never found in nature as a free element. Its only stable isotope, ⁸⁹Y, is also its only naturally occurring isotope.

In 1787, Carl Axel Arrhenius found a new mineral near Ytterby in Sweden and named it ytterbite, after the village. Johan Gadolin discovered yttrium's oxide in Arrhenius' sample in 1789, and Anders Gustaf Ekeberg named the new oxide yttria. Elemental yttrium was first isolated in 1828 byFriedrich Wöhler.

The most important use of yttrium is in making phosphors, such as the red ones used in television set cathode ray tube (CRT) displays and inLEDs. Other uses include the production of electrodes, electrolytes, electronic filters, lasers and superconductors; various medical applications; and as traces in various materials to enhance their properties. Yttrium has no known biological role, and exposure to yttrium compounds can causelung disease in humans.

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Strontium

Strontium is a chemical element with symbol "Sr" and atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. Strontium has physical and chemical properties similar to its two neighbors calcium and barium. It occurs naturally in the minerals celestine and strontianite. While natural strontium is stable, the synthetic ⁹⁰Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.

Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered in 1790 by Adair Crawfordand William Cruickshank. The production of sugar from sugar beet was in the 19th century the largest application. Strontium compounds are today mostly used for the production of cathode ray tubes. The displacement of cathode ray tubes by other display methods in television sets is changing the overall consumption.

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Rubidium

Rubidium is a chemical element with the symbol "Rb" and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metalgroup, with an atomic mass of 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in Group 1, such as very rapid oxidation in air. Rubidium has only one stable isotope, ⁸⁵Rb. Another isotope, ⁸⁷Rb, which composes almost 28% of naturally occurring rubidium, is slightly radioactive with a half-life of 49 billion years—more than three times longer than the estimated age of the universe.

German chemists Robert Bunsen and Gustav Kirchhoff discovered rubidium in 1861 by the newly developed method of flame spectroscopy.

Rubidium's compounds have various chemical and electronic applications. Rubidium metal is easily vaporized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms.

Rubidium is not known to be necessary for any living organisms. However, like caesium, rubidium ions are handled by living organisms in a manner similar to potassium ions, being actively taken up by plants and by animal cells.

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Krypton

Krypton is a fictional planet in the DC Universe and the native world of Superman. In some stories, it is also the native world of Supergirl, Kryptothe Superdog, and Power Girl (albeit an alternate universe version in her case, designated "Krypton-Two"). Krypton has been portrayed consistently as having been destroyed just after Superman's flight from the planet, with exact details of its destruction varying by time period, writers and franchise. Kryptonians were the dominant species of Krypton.

The planet was created by Jerry Siegel and Joe Shuster, and was first referred to in Action Comics #1 (June 1938). The planet was given its first full-fledged appearance in Superman #1 (Summer 1939).

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Bromine

Bromine is a chemical element with the symbol "Br", and atomic number of 35. It is in the halogen group (17). The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826. Elemental bromine is a fuming red-brown liquid at room temperature, corrosive and toxic, with properties between those of chlorine and iodine. Free bromine does not occur in nature, but occurs as colorless soluble crystalline mineral halide salts, analogous to table salt.

Bromine is rarer than about three-quarters of elements in the Earth's crust; however, the high solubility of bromide ion has caused its accumulation in the oceans, and commercially the element is easily extracted from brine pools, mostly in the United States, Israel and China. About 556,000 tonnes were produced in 2007, an amount similar to the far more abundant element magnesium.

At high temperatures, organ obromine compounds readily convert to free bromine atoms, a process which has the effect of stopping free radical chemical chain reactions. This effect makes organobromine compounds useful as fire retardants; more than half the bromine produced industrially worldwide each year is put to this use. Unfortunately, the same property causes sunlight to convert volatile organobromine compounds to free bromine atoms in the atmosphere, and an unwanted side effect of this process is ozone depletion. As a result, many organobromide compounds that were formerly in common use—such as the pesticide methyl bromide—have been abandoned. Bromine compounds are still used for certain purposes, however, including in well-drilling fluids, in film photography, and as an intermediate in the manufacture of organic chemicals.

Bromine has no essential function in mammals, though it is preferentially used over chlorine by one antiparasitic enzyme in the human immune system. Organobromides are needed and produced enzymatically from bromide by some lower life forms in the sea, particularly algae, and the ash of seaweed was one source of bromine's discovery. As a pharmaceutical, the simple bromide ion, Br^–, has inhibitory effects on the central nervous system, and bromide salts were once a major medical sedative, before being replaced by shorter-acting drugs. They retain niche uses as antiepileptics.

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