Extraction and Structure of Gold - Research Paper Example

September 8, GOLD MATERIAL: EXTRACTION, STRUCTURE, PROPERTIES AND ITS IMPORTANT This paper gives a general overview of gold material, its physical and chemical structures and properties, the general process used in extraction of the mineral (gold) including the many types of gold we have. Also, it presents a view on the economic importance of the ore and also the general trend of the gold increasing demand since its discovery. Gold is the most expensive material and it’s not largely mined in many parts of the world. The paper will expound further on key areas where gold is found in plenty and what are the cautions undertaken in mining the gold to avoid any landslides due to pressure on the open ores left after the gold extraction. Introduction Gold is a dense element having a shiny, soft and malleable surface. Its chemical symbol is Au which comes from a Latin word Aurum. It has an atomic number of 79. Gold is among the non-reactive metal, thus, it many functional uses in manufacturing industries and natural environments. It has rust resistance i.e. does not react with oxygen. It is a good conductor of electricity being able to convey a very tiny electrical current in temperature ranging from -550 to +2000. 1 This metal is among the most ductile metals, thus, it allows to be molded into very small threads or wires without breaking. Furthermore, gold is malleable. This makes it possible to be shaped into extraordinary thin sheets. It is known to be the least absorptive material, but most reflective of infrared energy. Gold with a high purity has the capability of reflecting 99 percent of infrared rays. Also, gold is among the best heat conductors or thermal energy. This makes it to be used to transfer heat away from very delicate instruments, like electronics. Gold alloys, being the most tenacious and long performing material that is used to guard electronics against high temperatures produced by them. Place on earth where gold is mined include Australia, Alaska, Spain, South Africa (Witwatersrand) and other parts of Africa. South Africa remains one of the biggest gold producers in the world. Figure1. Sample image of gold in a pan taken from gold mine in Alaska. Its shinny and can be seen from a far distance in the pan. General properties Below table gives the major general properties of gold which are going to be discussed further and distinguished into chemical or physical classification. General properties of gold. Atomic Mass 196.9655 g.mol -1 Boiling Point 3129 K, 5173 °F, 2856 °C Standard potential +1,68 V ( Au+/ Au ) Ionic Radius 0.137 nm (+1) Vander Waal Radius 0.144 nm Density 19.3 g.cm-3 at 20°C Electronic Shell [ Xe ] 4f14 5d10 6s1 History Discovered Middle eastern (Before 6000 BC) Table1. The common properties of gold material, It shows both physical and also the chemical properties of gold. Occurrence in Nature It occurs in its compound and also in native state (It’s Free State). 2 Gold is not combined with any other element in nature. Telluride (a compound of element Tellurium) is the most common compounds of gold. For example, gold telluride (AuTe 2) is mostly composed of mineral calavarite. Also, gold is found in Nuggets and chunks large enough to see. 3 This enables people to mine gold by picking and collecting it from the rivers and streams. Gold estimation abundance in the earth crust is around 0.005 Parts per Million. 3 This makes a very small fraction as compared to Iron and other metals. Many people believe that, about 70 million tons of gold are found in oceans. This has led to many ocean exploration of gold by many individuals and also some hold a belief that around 10 billion tons of gold are found at ocean bottoms. Howevwer, no one has ever found a means or a mining way to exploit that bottom gold. Researchers are working extremely hard to discover a way to exploit that bottom ocean gold, dissolved in seawater. Figure2. Pieces of gold attached to a chunk of quartz. Gold is found in Nuggets and chunks large enough to see. 3 This enables people to mine gold by picking and collecting it from the rivers and streams. Isotopes Isotopy is the existence of an element in more than one form. Unlike other many elements, we have only one occurring gold isotope and this is gold-197 (197Au). This isotope is used in field of medicine to study the liver after it has been made into colloidal state (Consisting of fine particles in a liquid solution). It’s a radioactive isotope so once the colloidal is injected into the body of the person being under examination, it penetrates to the body organs such as the liver and hence special detectors are used to determine if the liver is functioning under normal state. The isotope can also be used to kill some cases of cancerous cells especially those which form in the stomach, Peritoneum. Physical properties of Gold It has a bright metallic yellow color as shown in figure 3. Gold is Ductile and malleable with density of 19.3 g cm-3. A piece of gold, around one gram can be hammered to produce around a meter in area of gold with around 250 Atoms thickness. 4 Gold ha the melting point (M.P) of 1337.33 [or 1064.18 °C (1947.52 °F)] K as compared to its Boiling Point of (B.P) 3129 [or 2856 °C (5173 °F)] K The Thermal conductivity of gold is 320 W m-1 K-1 and its Coefficient Linear Thermal Expansion is 14.2 x 10-6 K-1. It has an attractive luster and color which does not oxidize in presence of water or air. Its shiny surface is attributed to this property. 5 Gold can reflect yellow and red light therefore when its beaten to become transparent, the transmitted light always appears greenish-blue. It is placed in the solid state in the periodic table on the transitional metals, though its Liquid Range is 1791.67 K. Figure3. This shows the characteristic metallic yellow color of gold. Chemical properties of gold Gold is found in group 11 of the periodic table. It has an atomic mass of 196.96and Atomic number of 79.6 its symbol is AU. Its electron configuration is [Xe] 4f14 5d10 6s1 (2, 8, 18, 32, 18, 1), Figure 4. Figure4. Electron configuration of gold [Xe] 4f14 5d10 6s1 (2, 8, 18, 32, 18, 1), this places gold in group 11 of the periodic table. Gold is one of the most unreactive elements in nature. It does not react with halogens like chlorine, fluorine bromine etc. and also it does not react with water and it its simpler state. The chemical properties of gold make it to be used in various industries. Especially in manufacture of coins since it does not tarnish or corrode easily. Oxidation state of gold ranges from as low as -1 to +5 but +1 and +3 [Au(I) and Au(III)] are the most common gold oxidative states. 7 When reacted with mercury, it forms amalgamation rather than reacting to form a new compound. Its resistance to reaction of most of acids makes it not corrode easily. It’s a very good conductor of electricity thus it’s made to thin wires and used in electrical circuits. Use of gold electroplating in Copper Industries to make copper components improves its solder ability. Due to its ability to reflect heat and light, it is used in the construction of sky scrapers to reflect sunrays. Crystal Structure and x-ray diffraction Crystal structure means the arrangement of atoms in the gold structure. The crystal structure of gold is face centered cubic whereby Au-Au separation equals to around 288.4 pm which implies that the radius is 144.2pm. This contributes to gold being ductile (very high) hence the movement of dislocations is allowed in the lattice, see figure 5. X-ray diffraction is a type of radiation whereby the valence electrons of the gold crystal structure are scattered or the x-rays interacts with their spatial distribution. Gold has Self Assembled Monolayers structures of alkyl sulfides of which they are resolved by incidence x-rays diffractions for methylthiol and hexanethiol. The analysis of relative energies shows a completion between Self Assembled Monolayers as a result of van der Waals forces in the alkyl chains. The result of X-ray diffraction of gold yields these structures of the respective alkanethiols. Figure5. The face centered cubic of crystal structure of metallic gold. This contributes to gold being high ductile. Gold Mines Gold mines are usually characterized by very deep level of hard mining rock. The intrinsic mechanical complexity and the difficulties of labor intensive mining, working away at persistently declining grades, puts a huge amount of pressure on various corporations in this industry to intensify competence in relation to productivity improvements. For instance, high tonnage mined per mine worker and increased production volume as well as managing costs. Deep level mining is expensive to set up as an enterprise. Set up requires extremely large capital investment with specialized equipment. This type of enterprise is associated with long term investments. This has greatly affected entrepreneurs attempting to venture in gold mining business. As a result, there is limited supply of this commodity to the market due to low number of investors in the field. The mines range from small scale to large scale. The list below shows countries that has gold mines. a Pakistan, Reko Dik mine. b USA, Alaska c City of Gold in Canada d Welsh gold e Gold mine in Australia f Gold mine in China g Alsukari, new gold mine in Egypt h Gold mine in Witwatersrand, South Africa. Figure6. The super Pit gold mine in Australia, Australia remains to be one of the biggest gold mine country and also exporter in the world. Common uses of gold 1 Jewelry, this is the primary use of gold. It’s used to make ornaments and jewelry. 2 Financial Gold which includes Bullion, Coinage and Package 3 Used in manufacture of electronics 4 It is used in dental filling 5 Used in Aerospace- As lubrication, material in the aerospace vehicles due to its dependence. 6 It’s also used in Medicine especially in liver diagnosis. Conclusion Gold’s splendid characteristics of ductility, malleability, resistance to corrosion, reflectivity and good conductibility make it to be among the number one minerals that are used in the world. Despite these good characteristics of gold, the shortcoming in its production – increase in the cost of production- facilitates alternative elements such as nickel, silver, and steel to be used. Also, the mining of gold is associated with negative environmental effects. Many agencies on environment have come to protect over-exploitation of minerals such as gold since this material is considered as one of key economic indicator in the world. Gold prices have been going up since Second World War. According to Yahoo Finance, 5th April 2013, the gold price stands at 1558 against the US dollar per Ounce. 8 This is expected to rise in near future. Works Cited 1 Gold Mining and Sustainability: A Critical Reflection." Gold Mining and Sustainability: A Critical Reflection. N.p., n.d. Web. 03 Dec. 2012. . 2 Gold Chemical Element: Http:///www.Chemistryexplained.com/elements/c-k/gold.html 3 Gold Chemical Element: Http:///www.Chemistryexplained.com/elements/c-k/gold.html 4 Web Elements Periodic Table of the Elements: http://www.webelements.com/gold/physics.html 5 Messori, L; Marron, G. (2004). “Gold Complexes in the treatment of Rheumatoid Arthritis”. In sigel, Astrid. Metal ions and their complexes in Medication.CRM Press. Pp 280-301 6 Gold Chemical Element: Http:///www.Chemistryexplained.com/elements/c-k/gold.html 7 Buzzle; Chemical properties of gold. http://www.buzzle.com/articles/chemical-properties-of-gold.html Read More