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Gaffer Variety:
Elements 11 SN2 013:
By Willie Gaffer:
Silicon:
Silicon, Symbol Si, is a nonmetallic element occurring extensively in the earth's crust in silica and silicates. It makes up almost 28 percent of the earths crust. It is found in two forms, an amorphous and a crystalline allotrope. Recall that amorphous simply means it has no distinct crystalline structure. The atomic number is 14, the atomic weight is 28.086, the melting point is 1,410°C, the boiling point is 2,355°C, and the specific gravity is 2.33. The electron shell configuration is 2, 8, 4 and it has a valence of 4. It is in group 4A of the periodic table.
It is fair to say that without silicon there would be no
Silicon does not occur free in nature, but it is in practically all rocks as well as in sand, clays, and soils, combined either with oxygen as silica (SiO2, silicon dioxide). It also exists combined with oxygen and other elements such as aluminum, magnesium, calcium, sodium, potassium, and iron in the form of silicates. Its compounds also occur in all natural waters, in the atmosphere (as siliceous dust), in many plants, and in the skeletons, tissues, and body fluids of some animals.
Pure silicon is a hard, dark gray solid with a metallic luster and with a crystalline structure very similar to the diamond form of carbon. In fact, silicon shares many of the chemical and physical characteristics of diamonds. There is also a brown powdery form of silicon that has a microcrystalline structure. Silicon is extracted commercially by reducing the oxide in a reaction with coke in electric furnaces. On a small scale, silicon is produced from the oxide by reduction with aluminum.
Silicon is relatively inactive at ordinary temperatures, but when it is heated, it reacts with the halogens (fluorine, chlorine, bromine, and iodine) to form halides and with certain metals to form silicides. It is unaffected by acids except hydrofluoric. At red heat, silicon is attacked by water vapor or by oxygen, forming a surface layer of silicon dioxide.
There are three stable isotopes of silicon. Those are Silicon-28, silicon-29, and silicon-30. Five radioactive isotopes have also been discovered.
Phosphorus:
Phosphorus, Symbol P, is a highly reactive, poisonous, nonmetallic element occurring naturally in phosphates, especially apatite, and existing in three allotropic forms, white or yellow, red, and black. It is an essential part of protoplasm. It is used in safety matches, pyrotechnics, incendiary devices, fertilizers, poison (nerve) gas, and to protect metal surfaces from corrosion. The atomic number is15, the atomic weight is 30.9738, the melting point of the white form is 44.1°C, the boiling point is 280°C, and the specific gravity of the white form is 1.82. The electron shell configuration is 2, 8, and 5, and it has valences of 3 and 5. It is in group 5A of the periodic table.
There is a weird bit of history associated with this element. It seems phosphorus was first isolated in 1669 by Henning Brand. Brand was a amateur alchemist. How he managed to get phosphorous is the weird part. Hold your nose. He took 50 buckets of urine and let them stand until they putrefied and “bred worms.” Oh boy! He then boiled the urine down to a paste and heated it with sand, thereby distilling elemental phosphorus from the mixture. This guy must have had a really strong stomach. Anything for science, I guess.
Still phosphorus, which glows in the dark, was just a chemical curiosity until about a century later when it was found to be a component of bones. Reduction of bones with nitric or sulfuric acid formed phosphoric acid, from which phosphorus could be extracted. Today phosphorus is made from phosphate rock in electric furnaces.
Phosphorus is a colorless, semitransparent, soft, waxy solid. It has the interesting property that it combusts spontaneously when exposed to air whereupon it forms dense white fumes of the oxide. This makes it quite useful if signal flares.
Phosphorus is present in the fluids within cells of living tissues as the phosphate ion, PO43-. It is one of the most important mineral constituents for cellular activity. The genes, which direct heredity and other cellular functions and are found in the nucleus of each cell, are molecules of DNA (deoxyribonucleic acid), which all contain phosphorus. Cells store the energy obtained from nutrients in molecules of adenosine triphosphate (ATP). Calcium phosphate is the principal inorganic constituent of teeth and bones.
Phosphorus is not found free in nature, although it does appear in meteorites. It is found in compounds that are widely distributed in many rocks, minerals, plants, and animals. It is12th in abundance among the elements in the Earth's crust, making up about 0.10 percent of the crust. It always occurs as the phosphate ion. The chief commercial source is phosphate rock, an impure massive form of carbonate-bearing apatite. Apatite is a glassy calcium-phosphate mineral, belonging to a group that ranges from colorless to purple, green, or brown in color.
Phosphorus has about 10 forms (allotropes) that occur within three major categories: white, red, and black. White phosphorus has two variant forms. The alpha form is stable at ordinary temperatures. It has a cubic crystal structure. The beta form is stable below -78° C. It has a hexagonal crystal structure. White phosphorus is poisonous. Exposure to sunlight or to heat converts it to red phosphorus, which neither phosphoresces nor spontaneously burns in air. Black phosphorus is flaky like graphite and is made by subjecting white phosphorus to high pressures. It is chemically the least reactive form. White phosphorus has been used for military purposes as a source of smoke and to fill incendiary shells and grenades. Red phosphorus is used in preparing the striking surface for safety matches.
All naturally occurring phosphorus is the stable isotope, phosphorus-31. Radioactive phosphorus-32 has a half-life of 14.3 days; it is a useful tracer in studies of the life cycles of plants and animals.