[7/12/2014 21:37] +91 90 86 985450: Fluorine Classification: Fluorine is a halogen and a nonmetal Color: pale yellow Atomic weight: 18.998403 State: gas Melting point: -219.6 oC, 53.6 K Boiling point: -188.1 oC, 85.1 K Electrons: 9 Protons: 9 Neutrons in most abundant isotope: 10 Electron shells: 2,7 Electron configuration: 1s2 2s2 2p5 Density @ 20oC: 0.001696 g/cm3 Interesting Facts about Fluorine Henri Moissan, who first isolated fluorine, also produced the world’s first artificial diamonds by applying huge pressures to charcoal. Fluorine is the most chemically reactive element. It reacts, often very vigorously, with all of the other elements except oxygen, helium, neon and krypton. Fluorine is the most electronegative element. This means that in molecules fluorine attracts electrons more powerfully than any other element can. Hydrofluoric acid, HF, dissolves glass. Its fluoride ions have a high affinity for calcium and can cause death by interfering with the body’s blood calcium metabolism when absorbed through the skin. Appearance and Characteristics Harmful effects: Fluorine is highly toxic and corrosive. Characteristics: Fluorine is the most reactive and the most electronegative of all the elements. Fluorine is a pale yellow, diatomic, highly corrosive, flammable gas, with a pungent odor. It is the lightest halogen. It reacts violently with water to produce oxygen and the extremely corrosive hydrofluoric acid. Uses of Fluorine Fluorine and its compounds – mostly uranium hexafluoride – are used in processing nuclear fuel. Fluorochemicals, including many high-temperature plastics such as Teflon, are also made using fluorine. Compounds of fluorine, including sodium fluoride, are used in toothpaste and in drinking water to prevent dental cavities. Hydrofluoric acid can dissolve glass and is used to etch the glass in light bulbs and in other products. Chlorofluorocarbons (CFCs) were used in as refrigerants in air conditioning units and freezers but they have now been banned because they contribute to ozone depletion. Abundance and Isotopes Abundance earth’s crust: 585 parts per million by weight, 104 part per million by moles Abundance solar system: 500 parts per billion by weight, 30 parts per billion by moles Cost, pure: $190 per 100g Cost, bulk: $ per 100g Source: In nature, fluorine occurs mainly in the minerals fluorspar (CaF2) and cryolite (Na3AlF6). Commercially, production of fluorine involves the electrolysis of a mixture of molten potassium fluoride and hydrofluoric acid. Fluorine gas forms at the anode, and hydrogen gas at the cathode. Isotopes: Fluorine has 11 isotopes whose half-lives are known, with mass numbers 15 to 25. Naturally occurring fluorine consists of its one stable isotope [8/12/2014 17:41] +91 90 86 985450: Gallium Classification: Gallium is an ‘other metal’ Color: silvery-blue Atomic weight: 69.723 State: solid Melting point: 29.76 oC, 302.91 K Boiling point: 2200 oC, 2473 K Electrons: 31 Protons: 31 Neutrons in most abundant isotope: 40 Electron shells: 2,8,18,3 Electron configuration: [Ar] 3d10 4s2 4p1 Density @ 20oC: 5.907 g/cm3 Appearance and Characteristics Harmful effects: Gallium is considered to be non-toxic. Characteristics: Gallium is a silvery, glass-like, soft metal. It sits close to the non-metals in the periodic table and its metallic properties aren’t as obviously metallic as most other metals. Solid gallium is brittle and is a poorer electrical conductor than lead. The solid metal fractures conchoidally. (Conchoidally means like a shell – the fractured surfaces are curved like a sea shell.) Gallium has the second largest liquid range of any element and is one of the few metals that is liquid near room temperature (m.pt. 29.76 oC, 85.6 oF ), melting in the hand. The other metals with this property are cesium, francium and mercury. Bromine is the only non-metallic element that is liquid at or around room-temperature. Gallium liquid clings to or wets glass and similar surfaces. Gallium also has the unusual property that (like water) it expands as it freezes. Four other elements expand when they freeze; silicon, bismuth, antimony and germanium Uses of Gallium Low melting gallium alloys are used in some medical thermometers as non-toxic substitutes for mercury. Gallium arsenide is used in semiconductor production mainly for laser diodes, light-emitting diodes and solar panels. It is also used to create brilliant mirrors. Abundance and Isotopes Abundance earth’s crust: 19 parts per million by weight, 5.5 parts per million by moles Abundance solar system: 40 parts per billion by weight, 0.6 parts per billion by moles Cost, pure: $220 per 100g Cost, bulk: $ per 100g Source: Gallium does not exist free in nature and there are no minerals with any substantial gallium content. Commercially, most gallium is extracted as a byproduct of aluminum and zinc production. Gallium is also extracted from the flue dusts of coal. Isotopes: Gallium has 24 isotopes whose half-lives are known, with mass numbers 61 to 84. Of these, two are stable: 69Ga and 71Ga with natural abundances of 60.1% and 39.9% respectively [9/12/2014 21:00] +91 90 86 985450: Germanium Classification: Germanium is a metalloid Color: gray-white Atomic weight: 72.64 State: solid Melting point: 938 oC, 1210.6 K Boiling point: 2830 oC, 3103 K Electrons: 32 Protons: 32 Neutrons in most abundant isotope: 42 Electron shells: 2,8,18,4 Electron configuration: [Ar] 3d10 4s2 4p2 Density @ 20oC: 5.323 g/cm3 Appearance and Characteristics Harmful effects: Germanium is not known to be toxic. Characteristics: Germanium is a lustrous, hard, gray-white semi-metallic element with a crystalline and brittle structure. It is a semiconductor. Germanium and the oxide are transparent to infrared radiation. Germanium also has the unusual property that (like water) it expands as it freezes. Four other elements expand when they freeze; silicon, bismuth, antimony and gallium. Uses of Germanium The most common use of germanium is as a semiconductor. Germanium is used in transistors and in integrated circuits. It is used as an alloying agent and as a catalyst. It is also used in infrared spectroscopes and infrared detectors. Some germanium compounds are useful because they are toxic to bacteria but are harmless for mammals. Abundance and Isotopes Abundance earth’s crust: 1.5 parts per million by weight, 0.42 parts per million by moles Abundance solar system: 200 parts per billion by weight, 3 parts per billion by moles Cost, pure: $360 per100g Cost, bulk: $120 per 100gB Source: The main ore of germanium is germanite, which is about 7% germanium. Commercially, germanium is obtained as a byproduct of metal refining and from some coal ashes. Isotopes: Germanium has 24 isotopes whose half-lives are known, with mass numbers 58 to 85. Naturally occurring germanium is a mixture of five isotopes and they are found in the percentages shown: 70Ge (21.2%), 72Ge (27.7%), 73Ge (7.7%), 74Ge (35.9%) and 76Ge (7.4%). The most abundant is 74Ge at 35.9% [11/12/2014 00:05] +91 90 86 985450: Gold Classification: Gold is a transition metal Color: golden yellow Atomic weight: 196.9665 State: solid Melting point: 1064.18 oC, 1337.33 K Boiling point: 2850 oC, 3123 K Electrons: 79 Protons: 79 Neutrons in most abundant isotope: 118 Electron shells: 2,8,18,32,18,1 Electron configuration: [Xe] 4f14 5d10 6s1 Density @ 20oC: 19.32 g/cm3 Interesting Facts about Gold Gold is the most ductile of all metals, meaning it is the most suitable for drawing into wires. Amazingly, one ounce of gold can be drawn into a wire 1250 miles long (thickness 1 micron). This means that you could make a gold wire long enough to go around the earth with just 20 ounces of gold. Using metric units, one gram of gold could be drawn to a length of 66 km. Gold is also the most malleable of all metals, meaning it can be beaten into thinner sheets than any other metal. Gold can be beaten without any special difficulty to a thickness of 0.1 micron. A stack of one thousand sheets of 0.1 micron gold leaf is the same thickness as a typical piece of printer paper. Gold is one of the densest elements. A cube of gold with each side just 14.2 inches long would weigh a ton. (37.27 cm sides give a metric ton.) The six metals denser than gold are Os, Ir, Pt, Re, Np and Pu. The concentration of gold below Earth’s crust is about 100 times higher than the concentration in it. ‘The acid test’ has become part of everyday speech. It means a test whose result is absolutely certain. The first acid test was a drop of nitric acid on metal. Gold does not dissolve in nitric acid, so if a metal reacts with nitric acid, it is certainly not gold. The ‘acid test’ became popular in the 1849 Californian gold rush, when all sorts of shady characters tried their hand at selling fake gold. The total mass of gold ever extracted from Earth is 170 000 metric tons (at the beginning of 2012). This amount of gold would fill three and a half Olympic swimming pools. About 2500 metric tons of gold is now mined every year. Two-thirds of all the gold ever taken from the earth has been taken since 1950. (12) (13) Want to get rich quick? Nobel prize winning chemist Fritz Haber did, but not for personal gain; Haber tried to help the German economy by extracting gold from seawater, but could not do it profitably. As recently as the 1980s the oceans were thought to contain about 4 kg of gold for every cubic kilometer of water – that’s almost 1 kg or 2 lb of gold each for everyone on Earth today. Estimates of ocean gold keep falling, however, and it now seems likely that each cubic kilometer of ocean contains just 30 grams of gold (Nozaki, 1992). That’s 1 ounce of gold in every 264 billion gallons of water. If you could process seawater equal in volume to draining Lake Ontario, you would capture 48 kg of gold, worth less than $3 million at today’s gold price. You cannot put that amount of water – 1600 cubic kilometers – through any chemical extraction process for $3 million. But perhaps you have an idea? In the world-changing Gold Foil Experiment, Ernest Rutherford and his coworkers Hans Geiger and Ernest Marsden fired alpha particles at gold leaf. The experiment found that alpha particles were deflected as they passed through the gold more than they ought to have been if the gold atoms were made of smoothly spread matter. The gold leaf used in the experiment had been pressed to about 0.6 micrometers thick – that’s a thickness of about 2000 gold atoms. By 1911 Rutherford had concluded that atoms consist of a tiny, dense point of positive charge surrounded mostly by empty space in which negatively charged electrons are present. In the fourth century BC the Greek mathematician and philosopher Plato wrote: “all the gold which is under or upon the earth is not enough to give in exchange for virtue.” Appearance and Characteristics Harmful effects: Gold is considered to be non-toxic. Characteristics: Gold is an excellent conductor of heat and electricity. It is a soft, yellow, metal with a beautiful lustrous sheen. It is the most malleable and ductile of all the elements and a single gram can be beaten into a sheet one square meter sheet of gold leaf. Gold has a very high density, 19.32 g/cm3. (A tennis ball sized sphere of gold would weigh about 5.7 pounds (2.6 kilograms). Gold is not the densest natural element, however. That honor belongs to osmium, followed very closely by iridium. Tennis ball sized spheres of these elements would each weigh about 6.8 pounds (3.1 kilograms). Gold is unaffected by air, water, alkalis and all acids except aqua regia (a mixture of hydrochloric acid and nitric acid) which can dissolve gold. Gold does react with halogens. It will, for example, react very slowly with chlorine gas at room temperature to form gold chloride, AuCl3. If gold chloride is heated gently, it will decompose to release the pure elements again. Unusually for a metal, gold can also form compounds (aurides) in which its oxidation number is negative (-1). For example, gold can combine with cesium to form cesium auride, CsAu, and rubidium to form rubidium auride, RbAu. These are ionic compounds with non-metallic properties in which the Cs or Rb ions are charged +1 while the Au atoms are charged 1-. Uses of Gold Gold is widely used in jewelry and coinage. It is also used in dental work as crowns, as gold plating for decoration and as gold thread in embroidery work. The gold content in alloys is usually measured in carats (k), with pure gold defined as 24k. Many satellites carry gold-coated mylar sheets as a solar heat shield because gold is an excellent reflector of radiation and unreactive. Similarly astronaut’s helmet visors are coated with a thin layer of gold to guard against dangerous effects of solar radiation. Gold is used widely in microelectronic circuits to ensure reliable, corrosion-resistant and static-free performance. The isotope 198Au, with a half-life of 2.7 days, is used for treating cancers – especially of the bladder, cervix, and prostate. Gold flake is added to some gourmet sweets and drinks. Chloroauric acid (HAuCl4) is used in photography for toning the silver image. Abundance and Isotopes Abundance earth’s crust: 4 parts per billion by weight, 0.4 parts per billion by moles Abundance solar system: 1 part per billion by weight, 10 parts per trillion by moles Cost, pure: $5540 per 100g Cost, bulk: $3800 per 100g Source: Gold is found underground and in rivers. The river deposits arise when gold that was rock-bound is released by erosion of the surrounding rock by running water. Gold is usually found as a metal alloyed to some degree with silver or sometimes with mercury as an amalgam. Gold nuggets found on Earth range from sizeable nuggets through tiny grains in alluvial (river) deposits to microscopic pieces in rocks. Commercially, gold is purified by cyaniding, amalgamating with mercury, or smelting processes. Further refining, which produces nearly pure gold, is usually by electrolysis. Isotopes: Gold has 35 isotopes whose half-lives are known, with mass numbers 171 to 205. Naturally occurring gold consists of its one stable isotope, 197Au
Posted on: Sun, 11 Jan 2015 03:48:48 +0000
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