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WHEN THINGS WERE WORKED OUT
Every milestone on an element profile, every turning point in a discovery history and every historical investigation, gathered into one series from -3000 to 2024. Each entry quotes the record that authored it and links back to it.
310 of 310 events
Silver mining is documented in parts of the eastern Mediterranean.
Silver · historyapproximate date
An Egyptian papyrus mentions the antimony sulfide pigment.
Antimony · historycentury date
Surviving Egyptian artifacts document ancient use of tin itself.
Tin · historyapproximate date
Silver extraction at Laurium became important in ancient Greece.
Silver · historyapproximate date
Antimony-containing yellow pigments were used in Babylonian decorative glazes.
Burial goods show that people worked platinum-containing materials.
Platinum · historyapproximate date
The wrought-iron pillar illustrates sophisticated early metalworking and exceptional preservation.
Iron · historyapproximate date
Albertus Magnus is credited with isolation, with historical uncertainty.
Arsenic · historycentury date
Agricola describes bismuth separately from more familiar metals.
Bismuth · historydecade date
Processed barite drew attention for its luminescence.
Barium · historydecade date
Concentrated sunlight destroyed diamond in Averani and Targioni’s experiments.
His observations contributed to later European scientific discussion.
Brandt published his investigation establishing cobalt as a distinct metallic constituent.
Pott’s chemical investigation separated the identity of the black mineral from the assumption that it contained iron.
Johann Heinrich Pott showed that the investigated manganese oxide was not an iron material.
Marggraf demonstrated zinc preparation within the developing framework of European chemistry.
Cronstedt identified nickel while studying the mineral now called nickeline.
Claude François Geoffroy distinguishes bismuth from lead and tin.
Black differentiated magnesia from lime through chemical investigation.
What would make a mortar suitable for a lighthouse repeatedly exposed to seawater?
Historical evidencerange date
Cavendish and Priestley investigated air after removing its oxygen component.
Nitrogen · historydecade date
Cavendish established that the collected gas differed from other known gases.
Kaim described producing manganese metal in a dissertation, a qualification to the conventional 1774 attribution.
Rutherford reported the properties of the residual gas in his doctoral work.
The Smithsonian identifies this as the year of Scheele’s independent oxygen discovery; his book appeared in 1777.
Scheele prepared the gas and recorded its properties, but interpreted it as a compound rather than an element.
Priestley prepared and investigated a gas that supported stronger combustion.
Scheele investigated the ore’s chemistry; Gahn obtained the metal by heating the oxide with charcoal.
Gahn prepared manganese metal after earlier work by several investigators.
His mercury-oxide experiment and subsequent visit to France helped bring the new gas into wider chemical debate.
Bergman's work strengthened the evidence that nickel was a distinct element.
Scheele distinguished molybdenite from graphite and lead minerals.
Hjelm obtained molybdenum and the Elhuyar brothers tungsten by high-temperature reduction of their oxides with carbon.
Metals that will not meltrange date
What evidence distinguishes a compound from a substance that merely looks simple?
Historical evidencerange date
Müller investigated tellurium-bearing gold ore.
Tellurium · historydecade date
Lavoisier’s Traité élémentaire de chimie presented the new system, with illustrations engraved by Marie-Anne Paulze Lavoisier.
Hope's examination helped distinguish strontium from related alkaline-earth materials.
Gregor identified an unfamiliar metallic constituent in a Cornish mineral.
Johan Gadolin identified an oxide in a mineral from Ytterby that did not match known earths, opening a line of investigation that would run for a century.
Gadolin recognized an unfamiliar constituent in the Ytterby mineral.
Vauquelin associated chromium with the green coloration of emeralds.
Chromium · historydecade date
Klaproth confirmed the new element and introduced tellurium.
Tellurium · historydecade date
Tennant identified carbon dioxide produced by burning diamond.
Vauquelin's work on crocoite established chromium through analysis and preparation.
Chromium · historyrange date
Vauquelin identified a previously unrecognised ingredient in beryl and emerald.
Del Río’s mineral finding was mistakenly attributed to chromium.
Hatchett and Ekeberg found two elements that most chemists then believed identical; Rose separated them again decades later.
Metals that will not meltrange date
Berzelius and Hisinger, and independently Klaproth, identified cerium.
William Hyde Wollaston separated two new metals from the soluble portion of crude platinum, identifying them by the distinctive salts they formed.
Wollaston recognized a distinctive salt in platinum-ore chemistry.
Smithson Tennant examined the insoluble residue and reported two further elements, one named for the strong smell of its oxide.
Wollaston published a fuller account of palladium.
Davy obtained potassium through electrochemical investigation of potash.
Humphry Davy passed current through moist potash and then soda, isolating two metals so reactive that they had to be kept away from air and water.
Potash salts supported established crafts.
Potassium · historyapproximate date
Joseph Louis Gay-Lussac and Louis Jacques Thénard produced sodium chemically.
Boron was obtained in the same period by chemical reduction rather than electrolysis, a reminder that the new method supplemented rather than replaced the older ones.
Davy's electrochemical work produced calcium and established the metal behind lime.
French and British researchers prepared impure boron-containing samples.
Heating and processing calcium-bearing stone supplied materials for mortar and plaster.
Calcium · historyapproximate date
The same electrical method, applied to their compounds, yielded calcium, strontium, barium and magnesium in impure form, extending the approach across a family.
An early claim associated with platinum residues was subsequently withdrawn.
Gay-Lussac and Thénard helped establish sulfur’s elemental identity.
Gay-Lussac and Thénard produced material containing elemental silicon.
Courtois observed a violet vapor in saltpetre manufacture; Gay-Lussac and Davy soon argued it was an element analogous to chlorine.
Further investigation and public reports supported identification of iodine.
Arfvedson recognized a previously unknown alkali element in petalite.
Berzelius distinguished selenium while investigating residue from acid manufacture.
Stromeyer identified cadmium through zinc-compound chemistry.
Berzelius prepared a relatively pure silicon sample and established its identity.
Berzelius obtained zirconium after earlier attempts at isolation had failed.
Ørsted obtained aluminum through chemical reduction of an aluminum compound.
Löwig obtained bromine from mineral-spring water before Balard's publication.
Balard isolated a dense red-brown liquid from the liquors remaining after sea salt crystallized.
Balard reported the new element after investigating concentrated salty water.
Wöhler developed the experimental preparation further and studied the metal.
Wöhler and Bussy separately obtained beryllium metal.
Sefström established vanadium through investigations associated with iron production.
Bussy prepared magnesium in an amount that made its metallic properties easier to investigate.
Mosander separated a new constituent from cerium-containing material.
Erdmann identified lanthanum in material from Norway.
Carl Gustaf Mosander showed that both ceria and yttria were mixtures, separating further components and establishing that apparent purity was not proof of it.
Fourteen elements hidden in one mineralrange date
Mosander described material later shown to contain several rare-earth elements.
Mosander distinguished yttrium-, terbium-, and erbium-associated oxides within earlier material.
Mosander distinguished oxide material during investigations of yttria.
Rose clarified its distinction from tantalum and proposed niobium.
Karl Ernst Klaus identified the last of the six in residues from Ural platinum ores, closing the group as it is now recognized.
Match production brought phosphorus into industrial manufacture.
Phosphorus · historycentury date
Bunsen and Matthiessen prepared enough lithium metal for fuller investigation.
Was access to air enough to make organisms appear in heated broth?
Historical evidencerange date
Bunsen and Kirchhoff established that each element emits a characteristic set of lines, making a flame spectrum a test for identity.
Two new elements were announced from lines in the residues of mineral water and of the mineral lepidolite, before either had been isolated in quantity.
Elements found by their colorsrange date
Crookes reports a new element from its green emission line.
Characteristic red spectral lines identified rubidium.
A green line led Crookes to thallium; an indigo pair led Reich and Richter to indium. Both elements were named for the color that revealed them.
Elements found by their colorsrange date
His textbook arranged elements using atomic weights and valence, before the familiar modern table existed.
Janssen and Lockyer observed a previously unexplained solar spectral line.
Mendeleev published a table with vacant places and detailed predicted properties for the elements he expected to fill them.
Filling the gaps the table left openrange date
Mendeleev published the periodic law in 1869; Meyer’s atomic-volume graph appeared in 1870.
Willoughby Smith's report of light-dependent conductivity stimulated published discussion and further experiments.
Lecoq de Boisbaudran found gallium by its violet lines, and its properties matched those Mendeleev had assigned to an empty place in the table.
Lecoq de Boisbaudran detected the spectral evidence and prepared the new metal.
Three elements were found whose measured properties matched the predictions, converting the table into an accepted law.
Filling the gaps the table left openrange date
Mendeleev predicted an element occupying the position below aluminum.
Gallium · historyapproximate date
Marignac, Auer von Welsbach and others resolved further pairs by repeated fractional crystallization, with spectra used to judge when a fraction had stopped changing.
Fourteen elements hidden in one mineralrange date
Delafontaine and Soret recognized unexplained rare-earth spectral lines.
Marignac identified a new fraction in erbium-containing material.
Nilson's mineral investigations revealed scandium as a distinct element.
Lecoq de Boisbaudran distinguished samarium using chemical separation and spectroscopy.
Marignac identified the rare-earth element later named gadolinium.
Auer von Welsbach distinguished praseodymium from neodymium.
A specimen from the Himmelsfürst mine prompted mineralogical and chemical analysis.
Lecoq de Boisbaudran distinguished the rare-earth constituent.
Moissan obtained elemental fluorine after earlier unsuccessful attempts by other investigators.
Moissan freed fluorine by low-temperature electrolysis of hydrogen fluoride in apparatus chosen so that the product would not consume it.
Winkler recognized the previously unexplained constituent as a new element.
Winkler’s analysis of argyrodite yielded the element that would later host the first successful transistor.
What separates obtaining a deposit from demonstrating a workable route to aluminum metal?
Historical evidencerange date
An international platinum–iridium length standard was sanctioned.
Rayleigh’s density investigations supplied the discrepancy that prompted the search for an unrecognized component of air.
Rayleigh and Ramsay connected the residual gas with a previously unknown element.
Ramsay identified terrestrial helium; work with Travers added neon, krypton, and xenon in 1898.
The missing ingredients of ordinary airrange date
Ramsay and, independently, Cleve and Langlet identified helium from minerals.
Becquerel observes penetrating radiation from uranium salts.
Becquerel’s photographic experiments established an emission that did not require continuing exposure to light.
The Curies report polonium after tracing activity in pitchblende.
Ramsay and Travers identified a new gas through its characteristic spectrum.
Ramsay and Travers isolated a new gas and observed its distinctive emission.
The Curies identify radium through radioactivity and chemical separation.
The Curies traced activity through successive fractions of pitchblende residues and announced two elements identified by that activity.
Schmidt and Marie Curie independently investigate thorium radioactivity.
Polonium and radium announcements followed chemical separations guided by radioactivity measurements. Bémont coauthored the radium report.
Debierne reported actinium from pitchblende residues; Dorn identified the gaseous emanation later named radon in the radium series.
Elements that arrive by decayrange date
Debierne announces a radioactive element from pitchblende residues.
Rutherford and Owens investigate a radioactive gas from thorium compounds.
Demarçay obtained europium from samarium-containing material.
Demarçay distinguished europium from samarium-containing material.
Giesel studies the material later recognized as the same element.
Further separation showed that early ytterbium material contained another element.
Independent investigations separated lutetium from ytterbium material.
Urbain and Auer von Welsbach independently separated ytterbium into two components, completing the naturally occurring series apart from the gap later filled by promethium.
Could a rare scattering event matter more than the direction taken by most particles?
Historical evidencerange date
Coolidge developed a working sequence that made sintered tungsten drawable into wire, enabling lamp filaments and X-ray targets.
Hunter obtained titanium metal of high purity after earlier mineral-based identification.
Marie Curie and André Debierne isolated metallic radium, years after the element’s initial identification.
Marie Curie receives the Nobel Prize in Chemistry for work including polonium and radium.
Fajans and Göhring identify a short-lived form of element 91.
Soddy proposed that chemically inseparable species of different mass occupy the same place in the table, and set out the radioactive displacement law.
Moseley connected characteristic X-ray frequencies with atomic number, providing a physical basis for element order.
Hahn and Meitner, and independently Soddy and Cranston, characterized protactinium; Perey identified francium as a rare branch of the actinium series.
Elements that arrive by decayrange date
Meitner and Hahn report work establishing the isotope now called protactinium-231.
Coster and Hevesy identified element 72 in zirconium ore by X-ray spectroscopy, where its atomic number said it should be.
Coster and Hevesy detected hafnium in zirconium mineral material.
A fellowship brought her into a research community with extensive stellar spectra and established classification work.
Reading the stars without confusing brightness with abundance
Walter and Ida Noddack and Otto Berg identified rhenium in platinum ores and columbite by X-ray spectroscopy.
Her dissertation connected observed spectra with physical conditions and inferred the dominance of hydrogen and helium.
Reading the stars without confusing brightness with abundance
Could differences between stellar spectra arise without radically different element mixtures?
Historical evidencerange date
A pure sample became available after earlier discovery and separation work.
Did making a long molecule automatically produce a practical textile fiber?
Historical evidencerange date
Harold Urey and colleagues identified the heavier stable hydrogen isotope.
Researchers obtained scandium metal through electrochemical preparation.
Element 43 was identified in cyclotron-bombarded molybdenum and element 61 among fission products; neither has a stable isotope.
Filling the gaps the table left openrange date
Berkeley experiments produce material that includes the new element.
McMillan and Abelson identified element 93 in bombarded uranium; Seaborg’s group produced element 94 soon after.
The team establishes plutonium as a distinct chemical element.
Seaborg proposed a second inner-transition series, which reorganised the bottom of the table and predicted how the new elements should separate.
What distinguishes a semiconductor that conducts from a device that amplifies a signal?
Historical evidencerange date
The discovery received public recognition after wartime secrecy.
Bardeen and Brattain achieved amplification on 16 December and demonstrated the device to Bell Labs officials on 23 December.
Could different behavior of blood cells be traced to a difference in their hemoglobin?
Historical evidencerange date
Shockley’s different architecture required subsequent process development before junction transistors could be produced in quantity.
Cyclotron bombardment produced elements 97 and 98; elements 99 and 100 were found in debris from a thermonuclear test.
Making elements beyond uraniumrange date
Spedding and colleagues advanced ion-exchange separation of rare earths.
Dysprosium · historyapproximate date
Test material yields evidence for fermium during subsequent analysis.
Fermium · historyrange date
Could ocean-floor magnetism distinguish a stationary crust from a spreading one?
Historical evidencedecade date
The Berkeley team identifies mendelevium using an einsteinium target.
Identification moved to a few atoms at a time, using elution position and decay signatures rather than bulk chemistry.
Making elements beyond uraniumrange date
Harvard promoted Payne-Gaposchkin to full professor and she became chair of astronomy.
Reading the stars without confusing brightness with abundance
Published research examined thulium-170 for radiography.
Production advances allow investigations using weighable quantities.
An optical transition in krypton-86 supplied the reference for a new definition of length.
NBS began distributing holmium oxide glass wavelength standards.
Bartlett challenged the supposed complete inertness of noble gases.
Berkelium dioxide is prepared, extending study beyond the initial tracer observations.
Could a scan across Venus distinguish radiation from a hot surface from a hot upper atmosphere?
Historical evidencerange date
Dubna and Berkeley experiments contribute to the discovery of element 104.
Rutherfordium · historyrange date
Competing Dubna and Berkeley experiments produced elements 104 to 106, opening naming disputes that took decades to settle.
The end of the seventh rowrange date
Dubna work establishes element 102 in the accepted discovery history.
Which measurements distinguish a high-voltage electrode from a usable rechargeable battery?
Historical evidencedecade date
Whittingham reported reversible lithium insertion into titanium disulfide in a cell using lithium metal.
Goodenough’s Oxford group established lithium cobalt oxide as a high-voltage positive-electrode material.
Cold fusion at Darmstadt produced bohrium, hassium, meitnerium, darmstadtium, roentgenium and copernicium, each identified by decay chains.
The end of the seventh rowrange date
Yoshino’s petroleum-coke design preceded commercial introduction of lithium-ion batteries in 1991.
A rechargeable battery built from several breakthroughsrange date
NBS studied degradation of terbium-chelate phosphors for stamp applications.
The international naming settlement retains lawrencium and the symbol Lr.
Dubna–Livermore experiments produce evidence for element 114.
Dubna, working with Livermore and Oak Ridge, produced elements 114 to 118 by hot fusion with a doubly magic beam.
The end of the seventh rowrange date
Sharpless’s Nobel-recognized work included osmium-based asymmetric oxidation chemistry.
GSI researchers observe formation of a volatile hassium tetroxide.
Experiments produce evidence for element 115, then publish the result.
Moscovium · historyrange date
The team observes its first candidate decay chain for element 113.
The collaboration publishes correlated decay evidence for element 118.
NASA published work on low-density nickel superalloy design.
Flerovium, Fl, is approved following recognition of the discovery in 2011.
CERN researchers report the first measurement of astatine’s ionization potential.
Researchers report commissioning a francium trapping facility at TRIUMF.
Oak Ridge reports newly produced plutonium-238 using neptunium feedstock.
Nihonium, Nh, is approved after recognition of the discovery in 2015.
Oganesson, Og, is approved following recognition of the discovery in 2015.
IUPAC approved the names nihonium, moscovium, tennessine and oganesson, filling the last four places in the row.
Berkeley researchers report mendelevium-244, extending the element’s isotope studies.
Researchers demonstrated europium-based luminescent codes on banknote specimens.
Researchers report structural and spectroscopic measurements of an einsteinium complex.
Laser spectroscopy reports trends in charge radii across fermium isotopes.
Combining copper with tin supported widespread manufacture of bronze tools and objects.
Cobalt-containing substances colored glass and ceramic objects before elemental identification.
People used mercury-bearing material long before modern elemental theory.
Early copper beads provide evidence of metalworking many millennia before modern chemistry.
Lead was extracted and used before written accounts of modern chemistry.
Iron was used before a single discoverer or modern discovery date could be recorded.
Zawar provides evidence of established zinc production before modern European identification.
Roman builders used lead extensively in pipes and related fittings.