Gold has many modern industrial uses including dentistry and electronics. Gold has traditionally found use because of its good resistance to oxidative corrosion and excellent quality as a conductor of electricity. Chemically, gold is a transition metal and can form trivalent and univalent cations in solutions. Compared with other metals, pure gold is chemically least reactive, but it is attacked by aqua regia (a mixture of acids), forming chloroauric acid, but not by the individual acids, and by alkaline solutions of cyanide. Gold dissolves in mercury, forming amalgam alloys, but does not react with it. Gold is insoluble in nitric acid, which dissolves silver and base metals. This property is exploited in the gold refining technique known as "inquartation and parting". Nitric acid has long been used to confirm the presence of gold in items, and this is the origin of the colloquial term "acid test", referring to a gold standard test for genuine value.
Gold is the most malleable and ductile of all metals; a single gram can be beaten into a sheet of 1 square meter, or an ounce into 300 square feet. Gold leaf can be beaten thin enough to become translucent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red. Such semi-transparent sheets also strongly reflect infrared light, making them useful as infrared (radiant heat) shields in visors of heat-resistant suits, and in sun-visors for spacesuits.
Gold readily creates alloys with many other metals. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors. Gold is a good conductor of heat and electricity and reflects infrared radiation strongly. Chemically, it is unaffected by air, moisture and most corrosive reagents, and is therefore well suited for use in coins and jewelry and as a protective coating on other, more reactive, metals. However, it is not chemically inert.
Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated out as gold metal by adding any other metal as the reducing agent. The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate.
High quality pure metallic gold is tasteless and scentless; in keeping with its resistance to corrosion (it is metal ions which confer taste to metals).
The base value of each unit of ranges between 10 and 30Ð per unit, with up to 2 units being found at any one time.
Presence on Mars: Very Rare
|Group 1 | Group 2 | Group 3 | Group 4 | Group 5 | Group 6|
|Group 2|||Argon | Bromine | Cadmium | Gallium | Germanium | Gold | Helium III | Krypton | Molybdenum | Neon | Niobium | Nitrogen | |Palladium | Rhodium | Rubidium | Ruthenium | Scandium | Selenium | Silver | Strontium | Technetium | Titanium | Vanadium | |Yttrium | Zirconium||