THE ELEMENT OF CARBON Carbon: Carbon has the chemical symbol C. It does not melt, but sublimes at about 3500C (it changes directly from a solid to a gas). Carbon's number is 6 and its atomic weight is 12.011. Its most common isotope (type of atom), carbon 12, was adopted in 1961 as the standard for atomic weights with an assigned weight of 12.0000. Carbon 14 provides archaeologists with a method of finding the age of many ancient objects. Carbon is one of the most important chemical elements. Industry uses it in a wide variety of products, and all living things are based on carbon. Without carbon, life would be impossible. Yet carbon makes up less than 0.03 per cent of the earth's crust. Pure carbon exists in nature in the form of diamonds, graphite, such as that used in some lead pencils, and fullerenes that are balls of pure carbon, of which the most common one is called the "buckyball" and is a sphere. All three are pure carbon, but with different crystal structures. Amorphous carbon, another form of pure carbon, consists of graphitelike particles too tiny to see without a microscope. There are over 1 million known carbon compounds. These compounds combine in various ways to produce an almost unlimited number of carbon-containing substances. Organic chemistry, which is the name given to the study of compounds made by and derived from living organisms, is primarily a study of carbon compounds. When materials containing lots of carbon, like wood, diamonds, oil, natural gas, are burned or heated without enough oxygen for them to burn completely a powdery-black soot of amorphous carbon, called carbon black, is formed. It is used in rubber products and paint. When heating bones without exposing them to air, animal charcoal or bone charcoal results. In the same way normal wood charcoal is made with wood. Coke, an important fuel used in making steel, results from heating soft coal without oxygen, as in making charcoal. Carbon burns readily and forms carbon dioxide. In this form it circulates between plants and animals in the process called the carbon cycle. Although less than one per cent of the world's mass is carbon, this cycle provides carbon enough for all life. DIAMONDS: In diamond, the carbon atoms are arranged in a close framework that makes diamond one of the hardest substances known. Diamonds are used to cut other hard materials. The molecules in diamonds are the same as those of charcoal or hard coal. But they are packed together in dense, clear crystals. Extreme pressure within the earth caused carbon to solidify into diamond. Diamonds made by Mother Nature are ordinarily made when carbon is squeezed at pressures of 750,000 pounds per square inch, causing the loosely structured atoms to rearrange themselves into the cramped configuration characteristic of Earth's most precious gem. "As chemists know", John Angus, one of the world's experts on the subject of growing synthetic diamonds at below sea-level pressures, says,"carbon in diamonds is arranged in five-atom, pyramidal shapes known as tetrahedrons. Each tetrahedron has a three-carbon triangular base, a one-carbon point, and carbon atom in the middle holding them together. A finished diamond is composed of networks of these structures and nothing else." John Angus makes artificial diamonds by chemical vapor deposition, using an ordinary welder's torch and its of acetylene gas. The flame heats a piece of metal, a disk of molybdenum, that is not allowed to get very hot by constantly cooling it. The carbon atoms in the oxyacetylene gas precipitate out of the flame and coalesce into tiny diamond crystals on the surface of the disk. When a gas is heated to such a high level for a long time the compound is slowly broken down and the carbon is left exposed. The carbons then combine into the most stable state at that temperature, which is the tetrahedron. (Diamonds in the rough, Discover, Mr '91) GRAPHITE: In contrast to diamond, graphite is very soft. So soft that it is widely used to lubricate moving machine parts. Its carbon atoms are arranged in flat sheets or layers that can easily slide back and forth over each other. The chief use of graphite is in foundries, where it gives a smooth facing to sand molds in which metal castings are made. Much is used also for crucibles, because it withstands terrific heat; and for electrotyping and electrical apparatus, because it is a good conductor of electricity. Other important uses are in paints, especially protective paints for structural ironwork, and in stove polish. Graphite films are used with scanning tunneling microscopes (STMs). In Feb.8 Science, Thomas P. Beeb Jr. and Carol R. Clemmmer cautioned people who use STMs to image biological molecules deposited onto a commonly used graphite substrate often mistake biological-looking features of the graphite surface for the biomolecules they aim to study. (One researcher's DNA is another's unicorn, Science News, S 14 '91) FULLERENES: The Buckyball, a 60-carbon spherical molecule, was discovered a few years ago, and it was said that this new compound would make new fibers that would have good mechanical properties and ought to have very few defects. The buckyball was would also make a good container for holding other atoms, said Mildred Dresselhaus, a physicist at MIT. These properties and ideas also hold for the larger all- carbon cousins of the buckyball, the fullerenes. There has been a lot of research done in the field lately because of the demand for new and better fibers. In a report in Applied Physics Letters, scientists of Northwestern University in Evanston, Ill. described a technique for making diamond films on silicon - an approach in which a thin layer of fullerenes increases diamond formation by almost 10 orders of magnitude over untreated silicon surfaces. Sumio Lijima of Fundamental Research Laboratories of NEC Corp. in Tsukuba, Japan, examined the carbon material that stayed stuck to the negative electrode typically used in making fullerene-filled soot. He discovered that those needlelike specks consist of nested graphite tubes. The needles grew to a length of 1 micrometer and contained up to 50 tubes. Lijima reports that the tubes grow so that they exhibit the same spacing as exists between the carbon layers in graphite. Dresselhaus states that the fibers probably start off as buckyball spheres that develop a defect as they form and so grow into cylinders. (Fullerene helps synthetic diamonds grow, Science News, N 16 '91) Mark M. Ross and his colleagues at the Naval Research Laboratory in Washington, D.C., made fullerenes with one or more yttrium atoms inside and studied them with two kinds of mass spectroscopy. They created the material by using a laser to vaporize yttrium powder in a chamber with graphite and fullerenes. The researchers suspect that the laser causes a fullerene molecule to open up and trap a metal atom, explains Ross. Sometimes, two or more of the opened, metal-filled fullerenes collide to from a larger molecule with multiple atoms inside. (Filling and fathoming fullerene molecules, Science News, D 14 '91). Other instances and reports have sprung up about atoms being trapped or placed in buckyballs or fullerenes, or fullerene polymers. Semeon J. Tsipursky, working with geochemist Peter R. Buseck at Arizona State University in Tempe, has found 60- and 70-carbon fullerenes in the film that lines tiny cracks of a shiny black rock called shungite. The researchers report the finding in the July 10 Science. They uncovered the first evidence that the round, all-carbon molecules called fullerenes occur naturally on Earth. (Fullerenes found in old rock, space. Science News, Jl 11 '92) Scientists often use lasers to make fullerenes by evaporating carbon atoms from graphite rods. But zapping fullerene films with lasers causes the 60-carbon buckyballs and their 70-carbon big brothers to vaporize and combine like soap bubbles, says Chahan Yeretzian, a physical chemist at UCLA. These united molecules sometimes billow to form stable fullerenes with 400 or more carbon atoms, he and his colleagues report in the Sept. 3 Nature. (Buckyballs combine to make giant fullerenes, Science News, S 5 '92) Less than a year after Lijima displayed the first photomicrographs of nanometer-size carbon cylinders to a crowd of amazed scientists, two of his colleagues have found a way to make the stupendously tough tubules by the gram. Buckytubes may be considered as "stretch" fullerenes; in effect, they consist of graphite sheets that have been spliced between two halves of a spherical fullerene. Together the long and the globular species constitute a third form of carbon, after diamond and graphite, that extends the element's reach throughout Euclid's empire. Diamond lives in three dimensions, graphite in two, buckytubes in one and buckyballs in none. This past March, Ebbeson and Ajayan discovered that by altering the pressure of the inert gas surrounding the arc and adjusting other parameters, they could deposit a hard lump of material about five millimeters in diameter on one of the electrodes. When they cracked open the lump, they found a core of nearly pure buckytubes. (Billions of Buckytubes, Scientific American, O '92). Other scientists have described this as "straws" JOURNAL 1.) Titanium: It is a metal common in nature. It is stainless, light, and as strong as steel - an ideal industrial metal. Titanium oxide, TiO2, is widely used as a paint pigment. 2.) Sodium: Is called Natrium in Latin. It is an alkali metal and behaves as lithium does. Sodium is the metallic element of common salt, NaCl. Many of its compounds are used as reagents in chemical laboratories. 3.) Manganese: It is a metal chiefly used, like vanadium, as a constituent of iron alloys. Mangenese dioxide, MnO2, is used in dry-cell electric batteries. Manganese forms compounds called permanganates containing the radical MnO4. Its compounds are all colored, most of them pink or purple. 4.) Arsenic: It is an example of the semimetallic elements. In its free form, arsenic forms a brittle, gray, crystalline mass. Arsenic forms two chief series of compounds, arsenates, containing the radical AsO4, and arsenites, containing the radical AsO3. White arsenic is arsenious oxide, As2O3. Calcium arsenate, Ca3(AsO4)2, is frequently used to poison insects that attack crops. 5.) Antimony: In Latin, stibium, is a semimetallic element, important as a constituent of the lead alloy called type metal. One compound of antimony, the sulphide, Sb2S3, is used in safety matches. 6.) Actinium: It is a metal about 150 times as radioactive as radium. The pure element provides an excellent source of neutrons for nuclear physicists. It is the first member of the actinide series of closely related elements. The series includes all the rest of the known elements. 7.) Bromine: Occuring in salt mines and ocean water, it is one of the two elements which are liquid under ordinary conditions, the other being mercury. The liquid is dark red and evil-smelling. Red vapor from it is highly irritating and poisonous. Lke other members of the halogen group, bromine is very active chemically. Sodium bromide, NaBr, is used in medicines, silver bromide, AgBr, in photography. Ethylene dibromide is one of the constituents of the Ethyl fluid used in high-test gaoline. 8.) Neon: It is an inert gas resembling helium in its properties. It is extracted from the air, which contains a very tiny percentage. This elements is used in orange-red neon signs. The light is produced by electrifying small quantities of the gas inside glass tubes. 9.) Iron: In Latin, ferrum, is the most widely used of all metals. It forms two important series of compounds, the ferrous compounds in which iron has a valence of two and the ferric compounds showing a valence of three. Ferrous chloride, FeCl2, and ferric chloride, FeCl3, are typical. When iron rusts, it combines with oxygen to from an oxide. Iron is the chief magnetic metal. 10.) Chromium: It is a gray metal of great hardness which takes a high, nontarnishing polish. It is much used for plating, chromium-plated surfaces being very resistant to scratching or wear. It is also used in alloys, chiefly with iron and nickel. Chromium forms compounds called chromates, containing the radical CrO4. These are of many colors and accound for the name chromium, from the Greek word for "color". 11.) Potassium: It is an alkali metal, behaves like lithium and sodium. It is seldom seen in its pure form. Important compounds of calium are the lime compounds, including quicklime, CaO; slaked lime, Ca(OH)2; calcium carbonate, CaCO3; and others. BIBLIOGRAPHY Compton's Pictured Encyclopedia, 1951, Compton & Company, Chicago. World Book, Discovery of the Elements, Science News, F 16 '91, N 16 '91, D 14 '91, S 5 '92, Jl 11 '92, D 19-26 '92 Scientific American, D '91, O '92, Discover, Mr '91 les too tiny to see without a mic]6XZR^!cLJ M9 z   G  9 y E  _ #`_%fT;|DS?EEGUW N7zUJDD I LCF`% g p #!d!!!("a""""B###$H$$$ %P%P%%% &J&&&&&&&&&6'w'''''9(|((((((#)e)))))*P***+R+n+p+r+++3,D,F,H,,, - -M-r-t-v---3.p...*/l/////0G000000'1'1e111#2426282w222?333333'4c444444444455555 5 5555555555 5"5$5&5(5*5*5,5.50525456585F5H5J5L5555555555666A6A6C6F6Y6[6]6]6m EDP%( -'14*5A6]6nopqrstuvwxyz{Page - &p