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Gaffer Variety:
Elements 17 SN2 019:
By Willie Gaffer:
November 5, 2007:
Gaallium:
Gallium, Symbol Ga, is a rare metallic element. The color is silver white. It is liquid near room temperature and expands on solidifying. It is a trace element found in coal, bauxite, and other minerals. The atomic number is 31, the atomic weight is 69.72, the melting point is 29.78°C, the boiling point is 2,403°C, and the specific gravity is 5.907. It has valences of 2 and 3. The electron configuration is 2, 8, 18, and 3. We find it in group 3A of the periodic table.
Gallium is one of the four metals that can be a liquid at or near room temperatures. The other three are mercury, cesium, and rubidium. Galliium has the longest liquid range of any metal making it useful I high temperature thermometers. One compound of gallium, gallium arsenide can convert electricity directly into light. This makes it useful in devices like light emitting diodes (LEDs).
The existence of Ggallium was predicted by Dmitri Mendeleyev in 1871 based on gaps in his newly created Periodic Table. The French chemist Paul Émile Lecoq de Boisbaudran using spectroscope later discovered it in 1875. Once he had found it, it was only a matter of time (about a year) before he isolated it chemically. GGallium does not occur free or concentrated in independent minerals, except for gallite, which is rare and not economically useful. It is extracted as a by-product from zinc blende, iron pyrites, bauxite, and germanite. It is normally a byproduct of the manufacture of aluminum. The purification of bauxite by the Bayer process results in concentration of gallium in the alkaline solutions. It can then be isolated using electrolysis.
Gallium is used to make high quality mirrors, to dope semiconductor materials, and in LEDs, as we said above. In one very unique application, huge masses of gallium are used to detect solar neutrinos through their reaction with the gallium.
Germanium:
Germanium, Symbol Ge, is a brittle, crystalline, gray-white metalloid element. It was the first material used for semiconductors. The atomic number is 32, the atomic weight is 72.59, the melting point is 937.4°C, the boiling point is 2,830°C, and the specific gravity is 5.323. It has valences of 2 and 4. The electron shell configuration is 2, 8, 18, 4. It occupies group 4A of the periodic table.
The name germanium was assigned by the German scientist Clemens Winkler, who discovered it in 1886. It is derived from the Latin word Germania, meaning Germany. This is another of the elements that were predicted by Dmitri Mendeleyev. Currently, germanium is produced as a byproduct of zinc smelting and from the burning certain types of coal. The largest use of germanium is in the semiconductor industry. When doped with small amounts of arsenic, gallium, indium, antimony or phosphorus, germanium is used to make transistors for use in electronic devices. Silicon has displaced germanium in many of the solid-state electronic devices. Germanium is also used in fluorescent lighting, in infrared optical devices, and in some alloys.
Arsenic:
Arsenic, symbol As, is a highly poisonous metallic element having three allotropic forms, yellow, black, and gray, of which the brittle, crystalline gray is the most common. The atomic number is 33, and the atomic weight is 74.922. Gray arsenic melts at 817°C, sublimes at 613°C, and it has a specific gravity of 5.73. It has valences of 3 and 5 and it is in group 5A of the periodic table. The electron shell configuration is 2, 8, 18, and 5.
Widely distributed on the earth, arsenic has been know to man for centuries. Since it sublimes when heated, it can be easily extracted from ores like arsenopyrite (FeAsS).
Arsenic and its compounds are used in insecticides, weed killers, solid-state doping agents, and various alloys.
Arsenic is used in glass manufacture of glass, as a hardener for lead products such as shot to eliminate a green color caused by impurities of iron compounds. One of he biggest uses has been in poison gas for military and as insecticides and herbicides for agricultural applications. Alloyed with gallium, it is used for doping semiconductor material. It is also used as pigments for paint and fireworks.
Arsenic is extremely toxic in very small doses making it very dangerous to humans and animals. This is compounded by the fact that doses can accumulate in the body leading to what is called chronic poisoning. Agricultural workers are at risk because they use insecticides and dusts containing arsenic, often breathing the vapors while they work.