Gold Crystal Structure
Gold belongs to the copper group of transition elements.
Atomic number: 79
Electronic configuration: [Xe] 4f14 5d10 6s1
Oxidation numbers: +1 +3
Atomic radius / pm: 144.2
Atomic Mass: 196.966569 (5)
Gold has been known since ancient times. The origin of its name comes from the Latin word for gold - aurum. It is a shiny metal of yellow color.
Gold is soft, malleable and ductile. It can be drawn in very thin sheets of only 5 nm (nanometers). It is rather stable in air as it does not react with oxygen even at elevated temperatures. Gold is insoluble in acids. Alkaline solutions also cannot harm it. Gold dissolves only in aqua regia (Royal water in Latin, a very strong acid) (HNO3: HCl = 1: 3) and some cyanide solutions containing oxygen.
Gold is a rare element and our planet has ten times less gold than silver. In nature, Gold is generally found in elemental form in the veins of flint or in sand rivers. It is used for jewelry production, for coins, dentures and electronic circuits and contacts.
ABUNDANCE in the atmosphere / ppm:
in the Earth's crust: 0.003 ppm
in the oceans: 0.000004 ppm
The face centered cubic unit cell of Gold.
Crystal Structure: face-centered cubic
The unit cell dimensions / pm: a = 407,833
Space group: Fm3m
Gold originates in hydrothermal ore veins, but can also be found in contact metamorphic deposits and in pegmatite rocks. As secondary deposits we have the placer deposits.
Gold occurs together with pyrite and arsenopyrite, sylvanite, quartz, calaverite, and krennerite. Beautiful specimens in a form of leaves and crystals are found Colorado Quartz mine, California.
Some of the rarest and most attractive forms of Gold are crystalline, skeletal Gold octahedra, up to 5 cm (2 inches). They have been found in alluvial sediments.
Some great looking crystals of Gold were discovered in the Ural mountain region in Siberia, Russia.
There is no other source of Gold except elemental gold itself. It is used in electronics, jewelry, and medicine.
Alloys of Gold
To use pure gold is not a great option for many applications. Because it is too soft. For most practical uses (e.g. application of gold in production of luxury items) you have to alloy it with other metals (usually copper and silver). Metals from the platinum group are also a good choice.
Unlike pure gold, the alloys of gold with other metals are in general much harder and much more resistant to abrasion. They can be used for making ornaments, Gold coins, and in the electronics industry (for contacts). Another field of application is optics (because good is great for reflection of infrared radiation).
Gold for coin production can be forged to have 1 to 10% copper.
For producing gold jewelry, it is an alloyed with silver and copper.
The so-called "Hard gold" is an alloy with only 1% of titanium, which greatly improves on its hardness.