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Cold is a chemical element in the periodic table that has the atomic 79. It has an atomic mass of 196.966 g/mol. It is represented by the symbol Au (from Latin: aurum). Aurum has 79 electrons, protons and 118 neutrons in its nucleus. It is a d-block element. The electronic configuration of gold is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s1. In the periodic table, it is group 11 and period 6. Its oxidation states are −3, −2, −1, 0, +1, +2, +3, +5 and its electronegativity is 2.54 (Pauling scale). The ionization energy for the removal of the first electron of gold is 890.1 kJ/mol and for the second electron is 1980 kJ/mol. It has only one stable naturally occurring isotope Au-197. It also has 36 radioisotopes.
Of all the metals it is the most malleable metal. In pure form, it is slightly reddish yellow. At STP gold is solid and has a density of 19.30 g/cm3. Its melting point is 1337.33 K ?(1064.18 °C, ?1947.52 °F) and its boiling point is 3243 K ?(2970 °C, ?5378 °F).
Most often it occurs as a native metal sometimes with silver as a gold-silver alloy (Electrum). It sometimes occurs to be within an alloy of mercury, copper and lead. It can be found in different minerals like sylvanite, calaverite, krennerite, nagyagite and petzite, and aurostibite. The world's largest producer of gold is china followed by Australia, Russia, the United States, Canada, and Peru. South Africa.
Gold has a wide range of applications. It is used as a currency for a long part of history. It is extensively used in Jewellery since its discovery. About 10% of new extracted gold goes to different industries. A large portion of it is used in electronics and computers such as electrical connectors in computers. Some salts and isotopes of gold are used in medicine these gold compounds have anti-inflammatory properties. Gold reflects electromagnetic radiation effectively. It is used for the reflection and coating of artificial satellites as well as in telescope mirrors. It is also used as food in the form of leaves, flakes or dust. It is labelled as E-175 for food additives.
It is a hypothesis that gold is produced during the collision of neutron stars and supernova nucleosynthesis. The process is called the r-process (rapid neutron capture). These gold particles were present in the dust of the solar system from which Earth and other solar systems came into existence.
There is no exact date, year or month of the discovery of gold. The early metal used by humans is thought to be gold because it is found in free elemental form (native). The earliest time recorded for the use of gold is the late Paleolithic period (Old stone age). Then in the pre-dynastic Egyptian period, it was extensively used in artifacts.