Gold

oro

Gold has been known since prehistoric times, and gold ornaments have been found in archaeological sites dating back more than 6,000 years. This was many centuries before copper, iron and other metals were learned to be purified. Gold is believed to be the first metallic element identified. It is a dense, non-reactive metal with a distinctive deep yellow color. Gold is found in nature in its pure state and rarely reacts to form compounds in nature. However, as an exception it is found forming gold telluride, AuTe2, in the mineral calaverite. Pure gold in nature can form nuggets, but mostly it is found as small specks embedded in rocks. Gold miners extract it by crushing these rocks and washing the gold dust away with water or strong acids. The most commonly used applications of gold include heat shields in astronaut visors. This metal has always been seen as valuable and many ancient objects, such as Tutankhamun's 3,300-year-old burial mask, are made of gold. Gold is also used to cover important buildings, such as temples. Today, this precious metal is more commonly used in jewelry or decoration.

Summary of properties (Au)

Atomic weight196.966570(4)
Discoverer (year)unknown (ancient times)
Natural formmetallic solid (face centered cubic)
Electron configuration[Xe] 414 5d10 6s1
Melting point (ºC)1064
Boiling point (ºC)2807
Abundance in earth's crust (ppm)0.004
Isotope (abundance)197Au (100)
Density g/cm319.32
Van der Waals radius (pm)214
Covalent radius (pm)130
Electronegativity (Pauling)2.54
Vaporization enthalpy (kJ/mol)324.00
Enthalpy of fusion (kJ/mol)12.55
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.13
Thermal conductivity (W/cm·K) at 25ºC and 1 atm3.170
Oxidation state+3, +1
Electron affinity (eV)2.31
1st Ionization potential (eV)9.2255

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