Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust, where it constitutes about 2% by mass, and ninth in the known Universe as a whole. This preponderance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Magnesium ion's high solubility in water helps ensure that it is the third most abundant element dissolved in seawater.

Magnesium is the 11th most abundant element by mass in the human body; its ions are essential to all living cells, where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNA. Hundreds of enzymes thus require magnesium ions to function. Magnesium is also the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers. Magnesium compounds are used medicinally as common laxatives, antacids (i.e., milk of magnesia), and in a number of situations where stabilization of abnormal nerve excitation and blood vessel spasm is required (i.e., to treat eclampsia). Magnesium ions are sour to the taste, and in low concentrations help to impart a natural tartness to fresh mineral waters.

Elemental magnesium is a fairly strong, silvery-white, light-weight metal (two thirds the density of aluminium). It tarnishes slightly when exposed to air, although unlike the alkali metals, storage in an oxygen-free environment is unnecessary because magnesium is protected by a thin layer of oxide that is fairly impermeable and hard to remove. Like its lower periodic table group neighbor calcium, magnesium reacts with water at room temperature, though it reacts much more slowly than calcium. When it is submerged in water, hydrogen bubbles will almost unnoticeably begin to form on the surface of the metal, though if powdered it will react much more rapidly. The reaction will occur faster with higher temperatures (see precautions). Magnesium also reacts exothermically with most acids, such as hydrochloric acid (HCl). As with aluminium, zinc and many other metals, the reaction with hydrochloric acid produces the chloride of the metal and releases hydrogen gas.

The name originates from the Greek word for a district in Thessaly called Magnesia. It is related to magnetite and manganese, which also originated from this area, and required differentiation as separate substances. See manganese for this history.

Magnesium is the seventh most abundant element in the Earth's crust by mass and eighth by molarity. It is found in large deposits of magnesite, dolomite, and other minerals, and in mineral waters, where magnesium ion is soluble. In 1618, a farmer at Epsom in England attempted to give his cows water from a well. They refused to drink because of the water's bitter taste. However the farmer noticed that the water seemed to heal scratches and rashes. The fame of Epsom salts spread. Eventually they were recognized to be hydrated magnesium sulfate.

The metal itself was first produced in England by Sir Humphry Davy in 1808 using electrolysis of a mixture of magnesia and mercury oxide. Antoine Bussy prepared it in coherent form in 1831. Davy's first suggestion for a name was magnium, but the name magnesium is now used.

Magnesium is a highly flammable metal, but while it is easy to ignite when powdered or shaved into thin strips, it is difficult to ignite in mass or bulk. Once ignited, it is difficult to extinguish, being able to burn in nitrogen (forming magnesium nitride), carbon dioxide (forming magnesium oxide and carbon) and water (forming magnesium oxide and hydrogen). This property was used in incendiary weapons used in the firebombing of cities in World War II, the only practical civil defense being to smother a burning flare under dry sand to exclude the atmosphere. On burning in air, magnesium produces a brilliant white light which includes strong ultraviolet. Thus magnesium powder (flash powder) was used as a source of illumination in the early days of photography. Later, magnesium ribbon was used in electrically ignited flash bulbs. Magnesium powder is used in the manufacture of fireworks and marine flares where a brilliant white light is required. Flame temperatures of magnesium and magnesium alloys can reach 5,610 °F, although flame height above the burning metal is usually less than 12 in. Magnesium may be used as an ignition source for thermite, an otherwise difficult to ignite mixture of aluminium and iron oxide powder.

Antimony

Antimony is a chemical element with the symbol Sb and an atomic number of 51. A silvery lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb₂S₃). Antimony compounds are prominent fire retardants found in many commercial and domestic products. Certain alloys are valuable for use in solders and ball bearings. An emerging application is the use of antimony in microelectronics. The relatively high toxicity of some antimony compounds, being similar to arsenic compounds, limits the applications.

An artifact made of antimony dating to about 3000 BC was found at Tello, Chaldea (part of present-day Iraq), and a copper object plated with antimony dating between 2500 BC and 2200 BC has been found in Egypt.  The first European description of a procedure for isolating antimony is in the book De la pirotechnia of 1540 by Vannoccio Biringuccio.  A text describing the preparation of metallic antimony that was published in Germany in 1604 purported to date from the early fifteenth century, and if authentic it would predate Biringuccio. The book, written in Latin, was called "Currus Triumphalis Antimonii", and its putative author was a certain Benedictine monk, writing under the name Basilius Valentinus. An English translation of the "Currus Triumphalis" appeared in English in 1660, under the title The Triumphant Chariot of Antimony. The work remains of great interest, chiefly because it documents how followers of the renegade German physician, Philippus Theophrastus Paracelsus von Hohenheim (of whom Thölde was one), came to associate the practice of alchemy with the preparation of chemical medicines.

Pure antimony was well known to Jābir ibn Hayyān, sometimes called "the Father of Chemistry", in the 8th century. Here there is still an open controversy: Marcellin Berthelot, who translated a number of Jābir's books, stated that antimony is never mentioned in them, but other authors claim that Berthelot translated only some of the less important books, while the more interesting ones (some of which might describe antimony) are not yet translated, and their content is completely unknown.

The first natural occurrence of pure antimony ('native antimony') in the Earth's crust was described by the Swedish scientist and local mine district engineer Anton von Swab in 1783. The type-sample was collected from the Sala Silvermine in the Bergslagen mining district of Sala, Västmanland, Sweden.

Antimony and many of its compounds are toxic, and the effects of antimony poisoning are similar to arsenic poisoning. Inhalation of antimony dust is harmful and in certain cases may be fatal; in small doses, antimony causes headaches, dizziness, and depression. Larger doses such as prolonged skin contact may cause dermatitis; otherwise it can damage the kidneys and the liver, causing violent and frequent vomiting, and will lead to death in a few days.

Lithium

Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable. For this reason, it is typically stored in mineral oil. When cut open, lithium exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a dull silvery gray, then black, tarnish. Because of its high reactivity, lithium never occurs free in nature, and instead, only appears in compounds, usually ionic ones. Lithium occurs in a number of pegmatitic minerals, but is also commonly obtained from brines and clays. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

The nuclei of lithium are not far from being unstable, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. As a result, they can be used in fission reactions as well as fusion reactions of nuclear devices. Due to its near instability, lithium is less common in the solar system than 25 of the first 32 chemical elements even though the nuclei are very light in atomic weight. For related reasons, lithium has important links to nuclear physics. The transmutation of lithium atoms to tritium was the first man-made form of a nuclear fusion reaction, and lithium deuteride serves as a fusion fuel in staged thermonuclear weapons.

Trace amounts of lithium are present in the oceans and in all organisms. The element serves no apparent vital biological function, since animal and plants survive in good health without it. Nonvital functions have not been ruled out. The lithium ion Li⁺ administered as any of several lithium salts has proved to be useful as a mood-stabilizing drug due to neurological effects of the ion in the human body. Lithium and its compounds have several industrial applications, including heat-resistant glass and ceramics, high strength-to-weight alloys used in aircraft, lithium batteries and lithium-ion batteries. These uses consume more than half of lithium production.

Nickel

Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four elements that are ferromagnetic around room temperature, the other three being iron, cobalt and gadolinium.

The use of nickel has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. Major production sites include Sudbury region in Canada, New Caledonia and Norilsk in Russia. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center, which makes the metal an essential nutrient for those life forms.

Because the ores of nickel are easily mistaken for ores of silver, understanding of this metal and its use dates to relatively recent times. However, the unintentional use of nickel is ancient, and can be traced back as far as 3500 BC. Bronzes from what is now Syria had contained up to 2% nickel. Further, there are Chinese manuscripts suggesting that "white copper" (cupronickel, known as baitung) was used there between 1700 and 1400 BC. This Paktong white copper was exported to Britain as early as the 17th century, but the nickel content of this alloy was not discovered until 1822.

In medieval Germany, a red mineral was found in the Erzgebirge (Ore Mountains) which resembled copper ore. However, when miners were unable to extract any copper from it they blamed a mischievous sprite of German mythology, Nickel (similar to Old Nick) for besetting the copper. They called this ore Kupfernickel from the German Kupfer for copper. This ore is now known to be nickeline or niccolite, a nickel arsenide. In 1751, Baron Axel Fredrik Cronstedt was attempting to extract copper from kupfernickel and obtained instead a white metal that he named after the spirit which had given its name to the mineral, nickel. In modern German, Kupfernickel or Kupfer-Nickel designates the alloy cupronickel.

In the United States, the term "nickel" or "nick" was originally applied to the copper-nickel Indian cent coin introduced in 1859. Later, the name designated the three-cent coin introduced in 1865, and the following year the five-cent shield nickel appropriated the designation, which has remained ever since. Coins of pure nickel were first used in 1881 in Switzerland.

After its discovery the only source for nickel was the rare Kupfernickel, but from 1824 on the nickel was obtained as byproduct of cobalt blue production. The first large scale producer of nickel was Norway, which exploited nickel rich pyrrhotite from 1848 on. The introduction of nickel in steel production in 1889 increased the demand for nickel and the nickel deposits of New Caledonia, which were discovered in 1865, provided most of the world's supply between 1875 and 1915. The discovery of the large deposits in the Sudbury Basin, Canada in 1883, in Norilsk-Talnakh, Russia in 1920 and in the Merensky Reef, South Africa in 1924 made large-scale production of nickel possible.

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. A tetravalent metalloid, silicon is less reactive than its chemical analog carbon. It is crystalline and reflective with bluish-tinged faces.

Silicon is the eighth most common element in the universe by mass, but silicon very rarely occurs as the pure free element in nature. It is more widely distributed in dusts, sands, planetoids and planets as various forms of silicon dioxide (silica) or silicates. In Earth's crust, silicon is the second most abundant element after oxygen, making up 27.7% of the crust by mass.

Silicon has many industrial uses. It is the principal component of most semiconductor devices, most importantly integrated circuits or microchips. Silicon is widely used in semiconductors because it remains a semiconductor at higher temperatures than the semiconductor germanium and because its native oxide is easily grown in a furnace and forms a better semiconductor/dielectric interface than any other material.

In the form of silica and silicates, silicon forms useful glasses, cements, and ceramics. It is also a constituent of silicones, a class-name for various synthetic plastic substances made of silicon, oxygen, carbon and hydrogen, often confused with silicon itself.

Silicon is an essential element in biology, although only tiny traces of it appear to be required by animals. It is much more important to the metabolism of plants, particularly many grasses, and silicic acid (a type of silica) forms the basis of the striking array of protective shells of the microscopic diatoms.

Plutonium

Plutonium is a synthetic transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and silicon. When exposed to moist air, it forms oxides and hydrides that expand the sample up to 70% in volume, which in turn flake off as a powder that can spontaneously ignite. It is also a radioactive poison that accumulates in bone marrow. These and other properties make the handling of plutonium dangerous.

The most important isotope of plutonium is plutonium-239, with a half-life of 24,100 years. Plutonium-239 and 241 are fissile, meaning the nuclei of their atoms can break apart by being bombarded by slow moving thermal neutrons, releasing energy, gamma radiation and more neutrons. It can therefore sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. Plutonium is the heaviest naturally-occurring or primordial element; the most stable isotope of plutonium is plutonium-244, with a half-life of about 80 million years, long enough to be found in trace quantities in nature. Plutonium-238 has a half-life of 88 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium-240 has a high rate of spontaneous fission, raising the neutron flux of any sample it is contained in. The presence of plutonium-240 effectively limits a sample's weapon potential and determines its grade.

Plutonium was first synthesized in 1940 by a team led by Glenn T. Seaborg and Edwin McMillan at the University of California, Berkeley laboratory by bombarding uranium-238 with deuterons. McMillan named the new element after Pluto, and Seaborg suggested the symbol Pu as a joke. Trace amounts of plutonium were subsequently discovered in nature. Discovery of plutonium became a classified part of the Manhattan Project to develop an atomic bomb during World War II.

Lead

Lead is a main-group element with symbol Pb (Latin: plumbum) and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air. It has a shiny chrome-silver luster when melted into a liquid.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, and is part of solder, pewter, fusible alloys and radiation shields. Lead has the highest atomic number of all stable elements, although the next element, bismuth, has a half-life so long (longer than the estimated age of the universe) it can be considered stable.

It is a dense, ductile, very soft, highly malleable, bluish-white metal that has poor electrical conductivity. This true metal is highly resistant to corrosion, and because of this property, it is used to contain corrosive liquids (e.g., sulfuric acid). Because lead is very malleable and resistant to corrosion it is extensively used in building construction, e.g., external coverings of roofing joints. Lead can be toughened by addition of a small amount of antimony or other metals. All lead, except ²⁰⁴Pb, is the end product of a complex radioactive decay. Lead is also poisonous, as are its compounds.

Zinc

Zinc is a metallic chemical element with atomic number 30. It is a first-row transition metal in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium because its ion is of similar size and its only common oxidation state is +2.

Zinc is the 24th most abundant element in the Earth's crust and has five stable isotopes. The most exploited zinc ore is sphalerite, a zinc sulfide; the largest exploitable deposits are found in Australia, Canada and the United States. Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC.

German chemist Andreas Sigismund Marggraf is normally given credit for discovering pure metallic zinc in a 1746 experiment. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of steel is the major application for zinc. Other applications are in batteries and alloys, such as brass.

Zinc is an essential mineral of "exceptional biologic and public health importance". Zinc deficiency affects about two billion people in the developing world and is associated with many diseases.

Radium

Radium is a radioactive chemical element which has the symbol Ra and atomic number 88.

The heaviest of the alkaline earth metals, radium is intensely radioactive. This metal is found in tiny quantities in the uranium ore pitchblende, and various other uranium minerals. When freshly prepared, pure radium metal is brilliant white, but blackens when exposed to air (probably due to nitride formation). Radium is luminescent (giving a faint blue color), reacts violently with water and oil to form radium hydroxide and is slightly more volatile than barium. The normal phase of radium is a solid.

Radium was formerly used in self-luminous paints for watches, nuclear panels, aircraft switches, clocks, and instrument dials. More than 100 former watch dial painters who used their lips to shape the paintbrush died from the radiation from the radium that had become stored in their bones. Soon afterward, the adverse effects of radioactivity became widely known. Radium was still used in dials as late as the 1950s. Although tritium's beta radiation is potentially dangerous if ingested, it has replaced radium in these applications.

During the 1930s it was found that workers' exposure to radium by handling luminescent paints caused serious health effects which included sores, anemia and bone cancer. This use of radium was stopped soon afterward. This is because radium is treated as calcium by the body, and deposited in the bones, where radioactivity degrades marrow and can mutate bone cells. The litigation and ultimate deaths of five "Radium Girl" employees who had used radium-based luminous paints on the dials of watches and clocks had a significant impact on the formulation of occupational disease labor law.

Radium was also put in some foods for taste and as a preservative, but also exposed many people to radiation. Radium was once an additive in products like toothpaste, hair creams, and even food items due to its supposed curative powers. Such products soon fell out of vogue and were prohibited by authorities in many countries, after it was discovered they could have serious adverse health effects. (See for instance Radithor.) Spas featuring radium-rich water are still occasionally touted as beneficial, such as those in Misasa, Tottori, Japan. In the U.S., nasal radium irradiation was also administered to children to prevent middle ear problems or enlarged tonsils from the late 1940s through early 1970s.