{"snapshot":"v2026.Q2","element":{"$schemaVersion":"element-v0","recordRevision":"2026-10-13","atomicNumber":79,"symbol":"Au","name":{"en":"Gold","es":"Oro","fr":"Or","de":"Gold","zh":"金","pt":"Ouro","ja":"金"},"cas":"7440-57-5","group":11,"period":6,"block":"d","category":"transition-metal","atomicMass":{"value":196.96657,"unit":"u","uncertainty":4E-05,"conditions":null,"sourceRef":"iupac-2021-atomic-weights"},"density":{"value":19.3,"unit":"g/cm^3","uncertainty":null,"conditions":"293.15 K","sourceRef":"crc-handbook-102"},"meltingPoint":{"value":1337.33,"unit":"K","uncertainty":null,"conditions":null,"sourceRef":"crc-handbook-102"},"boilingPoint":{"value":3129,"unit":"K","uncertainty":null,"conditions":null,"sourceRef":"crc-handbook-102"},"electronegativity":{"value":2.54,"unit":"Pauling","uncertainty":null,"conditions":null,"sourceRef":"crc-handbook-102"},"ionizationEnergies":[{"value":890.1,"unit":"kJ/mol","uncertainty":null,"conditions":null,"sourceRef":"nist-asd-gold"}],"electronAffinity":null,"electronConfiguration":{"shorthand":"[Xe] 4f14 5d10 6s1","expanded":"1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s1","shells":[2,8,18,32,18,1]},"termSymbol":null,"oxidationStates":{"common":[3],"all":[-3,-2,-1,0,1,2,3,5]},"commonCompounds":[{"formula":"AuCl3","name":"Gold(III) chloride","oxidationState":3,"classroomRelevance":"low","note":"Red crystalline solid; forms tetrachloroaurate(III) [AuCl4]- in HCl solution."},{"formula":"Au(OH)3","name":"Gold(III) hydroxide","oxidationState":3,"classroomRelevance":"low","note":"Brown precipitate; intermediate in some gold-refining processes."},{"formula":"AuCN","name":"Gold(I) cyanide","oxidationState":1,"classroomRelevance":"low","note":"Used in electroplating; central to the cyanide-leaching process for gold extraction."},{"formula":"Au2S","name":"Gold(I) sulfide","oxidationState":1,"classroomRelevance":"low","note":"Brown-black solid; one of few naturally occurring gold compounds."}],"reactivityNotes":"Gold is one of the least reactive metals. It does not react with oxygen, water, or most acids and bases at any temperature, which is why it is found in nature as the native metal and why it does not tarnish. It does dissolve in aqua regia (3:1 HNO3:HCl) to form HAuCl4, and reacts with chlorine gas, cyanide solutions, and mercury (forming amalgams).","isotopes":[{"massNumber":197,"symbol":"197Au","mass":{"value":196.96656879,"unit":"u","uncertainty":7.1E-08,"conditions":null,"sourceRef":"ame-2020"},"abundance":{"value":1,"unit":"fraction","uncertainty":null,"conditions":null,"sourceRef":"iupac-2021-isotopic-compositions"},"halfLife":{"stable":true},"decayModes":null,"spin":"3/2+","sourceRef":"nubase-2020"},{"massNumber":198,"symbol":"198Au","mass":{"value":197.96824242,"unit":"u","uncertainty":7.1E-08,"conditions":null,"sourceRef":"ame-2020"},"abundance":null,"halfLife":{"value":2.69464,"unit":"d","uncertainty":0.00014},"decayModes":[{"mode":"beta-","branchingRatio":1,"product":"198Hg"}],"spin":"2-","sourceRef":"nubase-2020"}],"spectroscopy":{"emissionLines":null,"nmrActiveIsotopes":[{"isotope":"197Au","spin":"3/2","receptivity":2.61E-05,"referenceCompound":"[Au(CN)2]- (aq)"}]},"discovery":{"discoverer":null,"year":"Antiquity","location":null,"etymology":"Old English 'gold'; chemical symbol Au from Latin 'aurum' (shining dawn). Gold has been worked continuously by humans for at least 6,000 years.","namedAfter":"Latin 'aurum' (shining dawn)"},"edu":{"oneLine":{"en":"A dense, soft, yellow precious metal so unreactive it is found in pure form in nature — and so easily worked that humans have used it for jewelry for over 6,000 years.","es":null,"fr":null,"de":null,"zh":null,"pt":null,"ja":null},"paragraph":{"en":"Gold is the canonical 'noble metal' — chemically inert under nearly all environmental conditions. It is exceptionally dense (19.3 g/cm³), highly malleable (one ounce can be hammered into a sheet 100+ ft² in area), and an excellent conductor of electricity. Most gold today is used in jewelry, in electronic contacts (corrosion resistance is critical), in dentistry, and as a financial reserve asset. Gold's unusual yellow color is a relativistic quantum-mechanical effect — the high-Z nucleus pulls 6s electrons into a lower energy orbital, shifting the absorption from UV (where most metals reflect uniformly) into the visible blue, so the reflected light is yellow.","es":null,"fr":null,"de":null,"zh":null,"pt":null,"ja":null},"misconceptions":[{"belief":"Pure gold and 24-karat gold mean the same thing as 14-karat gold.","reality":"Karat denotes purity. 24K is essentially pure (≥99.9%) gold; 18K is 75% gold by mass; 14K is 58.3%; 10K is 41.7%. The remainder is alloying metals (silver, copper, palladium) that add hardness and tune color. Pure gold is too soft for everyday jewelry, which is why most rings are 14K or 18K.","sourceRef":null},{"belief":"All metals with a yellow color are gold.","reality":"Pyrite (FeS2 — 'fool's gold'), chalcopyrite (CuFeS2), and brass (Cu-Zn alloy) all have a metallic-yellow appearance. Real gold is denser, softer, and chemically inert; pyrite shatters when struck whereas gold deforms; gold does not react with acids that dissolve copper or iron.","sourceRef":null},{"belief":"Gold is unreactive because of its electron configuration.","reality":"Gold's chemistry is unusual partly due to electron configuration but largely due to relativistic effects: the very heavy nucleus accelerates inner-shell electrons to a meaningful fraction of the speed of light, contracting and stabilizing the 6s orbital. The result is gold's color, its resistance to oxidation, and even its melting point being noticeably lower than the trend predicts.","sourceRef":null}],"demos":[{"title":"Density Comparison: 'Gold' Identification","level":"high-school","materials":["Several small metal samples of similar appearance (gold-colored brass, copper, pyrite, and — if available — a gold-plated or solid-gold object such as a tooth crown or jewelry piece)","Digital balance (0.01 g resolution)","Graduated cylinder (10 mL)","Water"],"procedure":["Mass each sample on the balance.","Fill the graduated cylinder partway with water and record the volume.","Submerge each sample in turn and record the new volume; subtract to get sample volume.","Calculate density (mass / volume) for each.","Compare against reference values: brass ~8.5 g/cm³, copper 8.96 g/cm³, pyrite ~5 g/cm³, gold 19.3 g/cm³."],"expectedObservations":"Solid gold is dramatically denser than any of the look-alike materials — roughly twice the density of brass or copper. Density is a definitive non-destructive test for gold. (Plated objects will give intermediate density depending on plating thickness and substrate.)","safetyNotes":["Wear safety goggles when handling small dense objects above the bench.","Dry samples thoroughly after the water-displacement step before returning them.","Do not use this lab as a tool for student valuation — refer real questions about jewelry to a professional assayer."],"ngssAlignment":["MS-PS1-3","HS-PS1-3"],"durationMinutes":30,"sourceRef":null}],"ngssTags":["HS-PS1-1","HS-PS1-3","MS-PS1-3"],"apTags":null,"relatedElements":["Ag","Cu","Pt","Hg"]},"sources":[{"id":"iupac-2021-atomic-weights","name":"IUPAC CIAAW Standard Atomic Weights 2021","url":"https://ciaaw.org/atomic-weights.htm","edition":null,"publisher":"International Union of Pure and Applied Chemistry","publishedYear":2021,"accessedDate":"2026-05-01","type":"primary"},{"id":"iupac-2021-isotopic-compositions","name":"IUPAC Isotopic Compositions of the Elements 2021","url":"https://ciaaw.org/isotopic-abundances.htm","edition":null,"publisher":"International Union of Pure and Applied Chemistry","publishedYear":2021,"accessedDate":"2026-05-01","type":"primary"},{"id":"ame-2020","name":"Atomic Mass Evaluation 2020 (AME2020)","url":"https://www-nds.iaea.org/amdc/ame2020/mass_1.mas20.txt","edition":null,"publisher":"AMDC / Chinese Physics C","publishedYear":2021,"accessedDate":"2026-10-13","type":"primary"},{"id":"nubase-2020","name":"NUBASE 2020 evaluation of nuclear properties","url":"https://www-nds.iaea.org/amdc/ame2020/nubase_1.mas20.txt","edition":null,"publisher":"AMDC / Chinese Physics C","publishedYear":2021,"accessedDate":"2026-10-13","type":"primary"},{"id":"nist-asd-gold","name":"NIST Atomic Spectra Database — Au","url":"https://www.nist.gov/pml/atomic-spectra-database","edition":null,"publisher":"National Institute of Standards and Technology","publishedYear":null,"accessedDate":"2026-05-01","type":"primary"},{"id":"crc-handbook-102","name":"CRC Handbook of Chemistry and Physics, 102nd Edition","url":null,"edition":"102nd","publisher":"CRC Press / Taylor & Francis","publishedYear":2021,"accessedDate":"2026-05-01","type":"primary"}],"editorialState":null}}