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Properties and uses of elements of the family aluminum
Aluminum is a lightweight, silvery metal, familiar to all households in the form of pots and pans, beverage cans and aluminum foil. It is attractive, non-toxic, corrosion resistant, nonmagnetic, and easy to train, cast iron, or the machine in a variety of forms. Aluminum is the third most abundant element in crust earth after oxygen and silicon, and is the most abundant of all metals. It constitutes 8.1 percent of the crust by weight and 6.3 percent of all the atoms in the crust. Because it is a very active metal, aluminum is never found in its metallic form. Rather, it is produced in a wide variety of earth minerals and rocks. Kaolin is particularly fine, white, aluminum containing clay that is used in the porcelain. Known as the aluminum in the other Anglo-Saxon countries, the element was named after alum mineral one of its salts have been known for thousands of years. Alum has been used by the Egyptians, Greeks and Romans as a mordant, a product using chemical dyes stick to cloth.
Pure aluminum is relatively soft and not a solid metal. When merging together with many other elements, it forms alloys with a wide range of useful properties. Aluminum alloys used in aircraft, road signs, bridges, storage tanks, and buildings. The world's tallest buildings, the towers of the World Trade Center in New York are covered with aluminum. Aluminum is used increasingly in automobiles because it is only a third heavier than steel and therefore reduces fuel consumption.
Despite the fact that aluminum is chemically very active, it does not corrode in humid air and made of iron. Instead, it quickly forms a thin film coating hard aluminum oxide. Unlike iron oxide or rust, flaking, aluminum oxide sticks firmly the metal and protects it from oxidation. The oxide layer is so thin that it is transparent, so the aluminum retains its metallic silver. Seawater, however, aluminum will corrode unless it was given an unusually thick oxide coating by the anodization process during the anodizing process, a piece of aluminum is oxidized in order to create a coating of aluminum oxide on its surface, which is able to make dyes, unlike the raw aluminum.
When aluminum is heated to high temperatures in a vacuum, it evaporates and condenses on any surface near as cool as glass or plastic. When evaporated on glass, He did a very good mirror. The aluminum has largely replaced the money in the production of mirrors because it does not tarnish and turn black as the money does when is exposed to impure air. A lot of food packaging materials and plastics are made of shiny new paper or plastic with a light coating of aluminum evaporated. The silver-colored balloons with helium popular at birthday parties are made of resistant plastic, covered with a thin evaporated coating of aluminum metal. Aluminum is one of the best conductors of electricity, with a conductivity of about 60 percent of that of copper. Because it is lightweight and highly ductile (able to be drawn thin son) it is used instead of copper in almost all the power lines of electricity transmission in many countries.
Aluminum is used to make pots and pots & pans because of its high thermal conductivity. It is handy as a food packaging sealed and waterproof with water because it is very malleable, it can be pressed between steel rollers to a sheet (a thin sheet) less than thousandth of an inch thick. Claims are made during that aluminum is toxic and aluminum pans is dangerous but no clear evidence of this belief has never been found. Much more widely used over the counter antacids contain thousands of times more aluminum (As aluminum hydroxide) that a person could never get to eat food cooked in an aluminum pot. Aluminum is the only light that has no known physiological function in the human body.
As a very reactive metal, aluminum is very difficult to separate other elements that are combined with it in its minerals and compounds. Despite its abundance on Earth, the metal itself has remained unknown for centuries. In 1825, slightly impure aluminum metal was finally isolated by the Danish physicist Hans Christian Oersted by treating aluminum chloride with a mixture of potassium (potassium dissolved in mercury). Then in 1827, the German chemist Hans Wöhler obtained from pure aluminum the reaction of potassium metal with aluminum chloride. It is generally given credit for the discovery of elemental aluminum.
But it was still very expensive to produce aluminum metal in any quantity and for a long time it remained a rare and precious metal. The big breakthrough came in 1886 when Charles M. Hall, a student of 23 years at Oberlin College in Ohio, and Paul LT. Héroult, another student in France, independently invented what is now known as the Hall or Hall-Héroult. This process is to dissolve the alumina (Aluminum oxide) in molten cryolite, a common mineral containing aluminum and then passing an electric current through the hot liquid. Aluminium Metal melt collects at the cathode (negative electrode). Shortly after the development of this process, the price of aluminum metal has fallen to about 30 cents a pound. The process used to extract aluminum from its ores today is essentially the same as that developed by Hall and Héroult 150 years ago.
Elemental boron occurs in a variety of forms ranging from light red crystals of a black powder or brown a transparent black crystal which is almost as hard as diamond. The element is never found free in the wild but it is extracted commercially from minerals such as borax, ulexite, colemanite and kernite. Boron is a relatively rare element, constituting about 0.001 percent of Earth's crust. It ranks number 38 in abundance after nitrogen, lithium and lead, but before bromine, uranium, and tin.
The physical properties of boron is a little difficult to determine since the element occurs in so many different forms. Chemically boron is an element fascinating. A text on claims that the chemical elements in inorganic chemistry of boron is "more diverse and complex than any other the periodic table. "The element forms five types of compounds: metal borides (1) (a metal in addition to boron), (2) boron hydrides (Boron plus hydrogen), (3) trihalides boron (boron, more than a halide, a halide is a halogen compound simple) oxo compounds (4) (and more complex boron oxygen radicals, a radical is a group of atoms that behaves as a unit in chemical reactions, but is not stable except as part of the compound), and organoboron compounds (boron combined with an organic or carbon-containing component).
Boron itself has relatively few uses outside of its role in nuclear reactors as a neutron absorber and in alloys as a hardening agent. It is also used in the manufacture of semiconductors. Composed his most famous, borax is used as a softening agent water in the production glass and ceramics, and as a herbicide. A compound derived from borax, boric acid is used as eye and in the production of heat resistant glass. Boron carbide and boron nitride are two boron compounds of particular interest. Both are used as refractory materials that are very heat resistant. When the boron nitride powder is compressed to very high pressures, it produces a hard crystalline, which is also harder than natural diamond.
For most of its history, the gallium is best known for an unusual physical property: it has a melting point of 29.76 ° C (85.6 ° F) lower than that of the human body. If we were to hold a piece of metal gallium in our hands, it would melt. Despite this Indeed, the gallium and its compounds have traditionally had few uses until recently. In the 1970s, a compound called gallium gallium arsenide was found to have semiconducting properties. Gallium arsenide has also been widely used in light emitting diodes (LEDs), which are used in electronic displays for calculators, watches and CD players. Neither indium nor Thallium has many commercial applications. The first element is mainly used in the manufacture of alloys and in the production of transistors and photocells. A radioactive isotope of the latter, thallium-201 is used in medical diagnostic studies, particularly those involving the function of the circulatory system.
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