[j Ρ n] Pronunciation: [jρn].
Gold (Aurum) is a metallic element with the symbol of Au and the atomic number of 79.
The simple substance (free form) of gold, commonly known as gold, is a precious metal, which has been used as currency, preservation and jewelry for many centuries. In nature, gold exists in the form of simple substance in gold nuggets or rocks, underground veins and alluvium. Gold is also one of the currency metals.
Gold is solid at room temperature, with high density, softness, brightness and corrosion resistance. It is the metal with the best ductility, second only to platinum.
Gold is a transition metal, which can form +3 and+1 valence compounds. Gold is chemically inactive, but it can be corroded by chlorine, fluorine, aqua regia and cyanide. Gold can be dissolved by mercury to form gold amalgam; Nitric acid that can dissolve silver cannot dissolve gold. The above two properties become the basis of gold refining technology, which are called "adding silver to divide gold" and "separating gold from silver" respectively.
The main uses of gold are:
1, used as international reserve. This is determined by the monetary commodity property of gold. Because of its excellent characteristics, gold has played a role as a currency in history, such as a measure of value, a means of circulation, a means of storage, a means of payment and a world currency.
Since the decoupling of gold and the dollar in 1970s, the gold function of money has also weakened, but it still maintains a certain monetary function. Gold still occupies a very important position in the international reserves of many countries, including major western countries.
2, used as jewelry decoration. Gorgeous gold ornaments have always been a symbol of one's social status and wealth.
3. Application in industry and science and technology. Because of its unique good performance, gold has extremely high corrosion resistance stability; Good electrical and thermal conductivity; The gold nucleus has a large effective cross section to capture neutrons; The reflection ability of infrared ray is close to100%; It has various catalytic properties in gold alloys.
Gold also has good manufacturability and can be easily processed into ultra-thin gold foil, micron gold thread and gold powder; Gold is easy to be plated on the surface of other metals, pottery and glass, and it is easy to be welded and forged under certain pressure. Gold can be made into superconductors and organic gold.
It is precisely because of its many beneficial properties that it has reason to be widely used in the most important modern high-tech industries, such as electronic technology, communication technology, aerospace technology, chemical technology, medical technology and so on.