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.

Other functions of gold

Although gold will be corroded by chlorine gas, it is widely used in the electronic industry because of its high conductivity, high oxidation resistance and environmental erosion resistance (including the ability to resist other non-hydrochloric acid), so as to make wire joints have good connections. Such as voice, image and universal serial bus connection. But the use of gold wire is controversial. It is often criticized by audio-visual experts as unnecessary and regarded as a marketing trick.

The connectors of some electronic measuring instruments are also plated with gold to avoid oxidation. However, gold is still very common in other application fields, such as high humidity, high corrosive atmospheric electronic contact and high failure rate contact, such as some computers, communication equipment, spacecraft and jet engines, and it is unlikely to be replaced by other metals in the future.