86 articles
Actinide
The actinide, or actinoid, series comprises 15 radioactive metallic elements with atomic numbers 89 to 103, from actinium through lawrencium, in which the 5f shell is filled.
Actinium
Actinium (element 89) is a soft, silvery-white radioactive metal, the first of the actinides, discovered by André Debierne in 1899 and best known through actinium-225, a leading radionuclide for targeted alpha therapy.
Allotropes of carbon
Allotropes of carbon, or carbon allotropes, are the different physical forms of the element carbon, the most common being graphite and diamond, joined after 1985 by fullerenes, graphene, and carbon nanotubes.
Ammonium
Ammonium, also known as the ammonium ion or azanium, is the positively charged NH4+ ion formed when ammonia accepts a proton, and a key nitrogen source in fertilizers.
Au
Au is the chemical symbol for gold, from the Latin aurum, a soft yellow metallic element with atomic number 79 that occurs natively and resists nearly all acids.
Buckminsterfullerene
Buckminsterfullerene, also known as C60 or a buckyball, is a hollow soccer-ball-shaped molecule of 60 carbon atoms discovered at Rice University in 1985 and honored with the 1996 Nobel Prize in Chemistry.
Bullion
Bullion is precious metal, most commonly gold, silver, platinum, or palladium, authenticated to a specified fineness and valued at the market price of its metal content, in bars and coins.
Cadmium
Cadmium (Cd, atomic number 48) is a soft, bluish silvery metal below zinc in group 12, used mainly in nickel-cadmium batteries and classified as a human carcinogen.
Cadmium poisoning
Cadmium poisoning is the toxic state caused by excessive exposure to cadmium, a cumulative heavy metal with a decades-long half-life that damages the kidneys and bones.
Cerium
Cerium (symbol Ce, atomic number 58) is a silvery lanthanide metal, the most abundant rare earth element, identified in 1803 and named after the asteroid Ceres.
Chromium
Chromium is a hard, silvery transition metal with symbol Cr and atomic number 24, discovered by Louis Nicolas Vauquelin in 1798 and best known for making stainless steel stainless.
Cobalt
Cobalt (symbol Co, atomic number 27) is a hard, silvery-blue, ferromagnetic transition metal, best known for deep blue pigments used since antiquity and its role in vitamin B12.
Colored gold
Colored gold is gold given a color other than its natural yellow, achieved by alloying, forming intermetallic compounds like purple AuAl2 and blue AuIn2, or surface treatments that produce black, brown, and blue finishes.
Copper
Copper is a reddish-gold metal, atomic number 29, the primary metal of the alloys brass and bronze, which gave the Bronze Age its name and today serves mostly in wiring and the power grid.
Crystal field theory
Crystal field theory (CFT) is an electrostatic model that explains the colors and magnetic behavior of transition metal complexes by splitting the metal's d orbitals, formulated by Hans Bethe in 1929.
Cubic crystal system
The cubic crystal system, also called the isometric system, is one of the seven crystal systems, defined by equal edges meeting at right angles and including primitive, body-centered, and face-centered lattices.
Cupronickel
Cupronickel, also written copper-nickel or white copper, is an alloy of copper and nickel, copper dominant, best known for coinage and for seawater equipment such as ship condensers and heat exchangers.
Diatomic molecule
A diatomic molecule is a molecule made of exactly two atoms, either of the same element, such as H2 and O2, or of different elements, such as CO.
Dysprosium
Dysprosium, element 66, is a silvery heavy lanthanide metal discovered in 1886 and used mainly to make neodymium magnets heat-resistant in electric vehicles and wind turbines.
Electrum
Electrum, also called green-gold, is a naturally occurring gold-silver alloy whose color ranges from pale yellow to white, used for the first coins struck in Lydia around 650 BCE.
Erbium
Erbium is a chemical element with the symbol Er and atomic number 68, a soft silvery lanthanide metal used in fiber optic amplifiers, dermatology lasers, and pink glass.
Europium
Europium (Eu) is a soft, silvery lanthanide metal, element 63, named after Europe and best known as the red phosphor in color televisions and euro banknotes.
Fineness
Fineness is the content of a precious metal in an alloy, expressed in parts per thousand by mass, the standard measure for gold, silver, platinum, and palladium purity.
Gadolinium
Gadolinium, element 64 with symbol Gd, is a silvery lanthanide metal with the highest thermal neutron capture of any element and key use in MRI contrast agents.
Gold
Gold, a chemical element with symbol Au and atomic number 79, is a dense, soft yellow metal prized since prehistoric times as jewelry, coinage, and a store of value.
Gold bar
A gold bar, also known as a gold ingot, is refined gold cast or minted into a standardized shape, from 1-gram retail bars to 400-ounce wholesale bars.
Gold extraction
Gold extraction, also called gold processing, is the set of mining, concentration, and chemical processes used to recover gold from ore, dominated by cyanide leaching in industry and mercury amalgamation in artisanal mining.
Gold nugget
A gold nugget is a naturally occurring mass of native gold, ranging from a few grams to tens of kilograms, found in veins or concentrated in placer deposits.
Goldschmidt classification
The Goldschmidt classification, proposed by geochemist Victor Moritz Goldschmidt in the early 1920s, sorts elements into siderophile, chalcophile, lithophile, and atmophile groups by their preferred host phase.
Group 11 element
A group 11 element, also called the copper or gold group, is one of four chemical elements: copper, silver, gold, and synthetic roentgenium, with copper, silver, and gold known as the coinage metals.