Laval University

From the SelectedWorks of Fathi Habashi

2015

Metals through agesFathi Habashi

Available at: https://works.bepress.com/fathi_habashi/163/

Metals Through the Ages. Their Discovery and Isolation Fathi Habashi Laval University, Quebec City Canada Metall volume 69 2015

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People had inhabited the Earth for hundreds of thousands of years before they began to use metals. This was the Stone Age in which

the only tools available were pieces of wood, bone, flint, or sea shells. The ancient people used only those metals that were available without mining or chemical treatment, for example, pieces of native gold, silver, and copper, and rare pieces of meteoric iron. These were too small in quantity to be of any consequence.

The seven metals of antiquity

The ancient people knew only seven met-als: gold, silver, copper, iron, mercury, lead, and tin. There are reasons for the early availability of these metals:W Some of these metals occur in the native

state, for example gold and silver.W Oxides of copper, iron, tin, and lead

are readily reduced below 800 °C. Such

temperature can be attained by burning carbonaceous material.

W Some of these metals have low melting points, for example, lead and tin, while mercury is already liquid at room tem-perature, thus they are easy to recover. Impurities in a metal lower the melting point considerably; for example, iron containing 4% carbon already melts at 1100 °C while the pure metal melts at 1540 °C. Metals used by the ancient people were seldom pure. Brass, an alloy of copper with zinc, was prepared by smelting a copper ore and another ore known as calamine.

Gold

As civilization progressed, gold became an important metal in Egypt. The phar-aohs sent expeditions of ten of thousands of slaves and soldiers to mine gold in the Eastern Desert. They cast the metal and

produced beautiful artefacts. As early as the Fifth Dynasty (2690-2420 BC) the ancient Egyptians documented primitive metallurgical operations on wall paintings which show blow-pipes in use with small furnaces and later they depict the use of bellows so that a high temperature can be reached when air is blown in the fire by these means (Figure 1). They were able to hammer gold so that foils can be produced and used for gilding wood and stones.

Silver and lead

Silver occurs as native metal or an alloy with gold called electrum. The mines of Laurion

near Athens in ancient Greece supplied most of the silver which was mainly used to mint coins (Figure 2). Lead ores also con-tain silver and they were sometimes treated for silver. Lead was widely used in Roman times mainly in making pipes (Figure 3).

Copper and tin

Metallic copper was produced by the reduction of its oxide ores in primitive furnaces. Sinai in Egypt and Cyprus were the main producers. This is believed to be the first metal produced from oxides

Metals Through the Ages.Their Discovery and IsolationHabashi, F. (1)

Seven metals were known to the ancient people: gold, silver, copper, iron, mercury, lead, and tin. In the Middle Ages the metalloids arsenic, antimony, and bismuth were added. Platinum was later brought from South America then zinc and boron became known from the East. It was only in the eighteenth century that mineralo-gists, travellers, and analysts supplied mineral specimens from different localities to laboratories where they were analyzed and this resulted in the discovery of ura-nium, zirconium, yttrium, beryllium, and chromium. In the nineteenth century the bulk of metals became known mainly due to Swedish chemists. In the twentieth century the very rare remaining metals: rhenium and hafnium were discovered and isolated. In the meantime metals that do not occur in nature or occur only in infini-tesimal quantities: protactinium, technetium, francium, promethium, and the trans-uranium metals became known and were isolated. Reasons behind the discovery are analyzed.

Fig. 2: Ancient Greek coin

Fig. 3: Typical Roman street with lead pipe

Fig. 1: Ancient Egyptian wall paintings showing furnaces, manually operated bellows, melting, and casting of gold

Part 1

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by reduction around 4000 BC. An ancient copper ingot is shown in Figure 4. This was, however, slowly superseded by bronze – a copper alloy containing about 10% tin, easy to melt and to cast. Bronze was either produced by mixing tin pro-duced from its oxide by reduction, with metallic copper, or by reducing a mixture of copper ore with a tin ore; this period of civilization became known as the Bronze Age. A Roman tin ingot is shown in Fig-ure 5.

Iron

Iron became known much later than cop-per although iron ores are more abundant than copper ores, having colorful miner-als, and almost as easy to smelt. This may be due to the fact that copper can be shaped by cold-hammering, whereas iron must be hammered hot. The Iron Age began around 2000 BC and most probably the Hittites in Asia Minor were skilled in this technology. Not many iron objects resisted corrosion through time except perhaps the Iron Pil-lar of Delhi which was made in the fourth century AD (Figure 6).

Mercury

Mercury was recovered by heating cinna-bar ore which occurred in abundance in Spain and north of Italy. It was used as a sticking medium to gild copper statues

(Figure 7). Gold leaf adheres firmly on the shiny amalgamated copper surface.

The age of alchemy

When an alchemist (Figure 8) dipped a piece of iron into a solution of copper vitriol, i.e., copper sulfate, the iron was immediately covered by a layer of metallic copper. This apparent transmutation of iron into cop-per led the alchemists to be occupied with the transmutation of base metals into gold. Gold, the most noble of all metals was insol-uble in all acids or alkalies known at that time. The Arab alchemists of the eighth and ninth centuries, e.g., the Jabir Ibn Hayyan (720-813 AD) thought they could change iron into gold, a process which became known as the transmutation of metals. He discovered aqua regia, i.e., royal water is a mixture of HCI and HNO3 that dissolves

gold; neither of the acids alone has any dis-solving action on gold. Nothing worthwhile in the field of metallurgy took place during the dark ages of magic, superstition, and alchemy except that many acids and salts were prepared, described, and used for a variety of purposes.

The flow of knowledge from the East to the West

The art of making Toledo swords, famous for 200 years thrived under the Arabs in the eighth century A D. There was cultur-al contact between the Arabs in Damas-cus and the Indians, who excelled in iron making. It was only with the translation of Arabic texts into Latin, and henceforth the flow of alchemical knowledge to Europe in the tenth century, and the appearance of the Renaissance in Italy few centuries later, that the art of metal extraction started to take shape.

New metal discoveries

In the thirteenth and fourteenth centuries three new metalloids: arsenic, antimony, and bismuth became known in Europe in the elemental state and were described by

Fig. 4: An ancient copper ingot [British Museum]

Fig. 5: Roman tin ingot [Royal Museum in Truro, Cornwall]

Fig. 6: Iron Pillar of Delhi [fourth century AD]

Fig. 8: An alchemist at work

Fig. 9 and 10: Albertus Magnus (1193-1280) (left) and Georgius Agricola (1494- 1555)

Fig. 7: A once gilded bronze statue of Mar-cus Aurelius in Rome

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the German monk Albertus Magnus (1193-1280) (Figure 9) and others.

Mining and metallurgical literature

In the sixteenth century two important books on metallurgy appeared. The first “De La Pirotechnia” appeared in 1540; its author Vannoccio Biringuccio (1480-1538) was working in the Armoury of Siena in Italy, and had traveled widely through Ger-many and Italy. The book, written in Italian, was concerned with ores, assaying, smelt-ing, separating gold from silver, making of alloys, melting, casting, and fireworks. The second book “De Re Metallica” appeared in 1556; a year after the death of its author, Georgius Agricola (1494- 1555) (Figure 10) a medical doctor from Saxony who traveled widely in the mining districts in this area. The title means “Of things Metallic”; it was the reference book on mining and metal-lurgy for at least two centuries.

Fire Assaying

Control of the purity of gold and silver, and the prevention of counterfeiting of coins was always of primary importance to the administrators of the early com-munities. It is not surprising, therefore, that methods for analyzing gold and silver were developed. The earliest known pro-cedure which is still in use today, is known as the fire assaying was documented by Lazarus Ercker (1530-1594). In summary the material is melted with fluxes, litharge (PbO), and a reducing agent such as flour. The fluxes contained such ingredients as silica glass, salt, and borax. The gold and silver are collected in the lead formed by the reduction of litharge. The lead is then removed as oxide under oxidizing condi-tions in another step known as “cupella-tion” by absorption in the material of the cupel, and there remains a bead of gold and silver, to be weighed. The same principle was applied on large scale for the recovery of precious metals from lead ores.

Platina from South America

For centuries the American Indians in Ecuador in South America collected the silver-like metallic particles found near the river bed mixed then with gold to make jewellery. They were unable to melt these particles. After the Spanish Conquest, it was the Spanish naval officer Antonio de Ulloa (1716-1795) (Figure 11) who brought

attention to this metal when he visited this region. The Spaniards unable to melt these particles, they called them platina a diminutive of silver. It took nearly a cen-tury to identify and isolate the components of platina:W 1750: Brownrigg and Watson,

platinumW 1803: Tennant, osmiumW 1803: Tennant and Des Costils.

iridiumW 1803: Wollaston, rhodium and

palladiumW 1844 : Klaus, ruthenium

Metals from the east

The production of metallic zinc was described in a Hindu book written around 1200 AD. The new “tin-like” metal was made by indirectly heating calamine with organic matter in a covered crucible fitted with a condenser. Zinc vapor was evolved and the vapor was air cooled in the con-denser located below the refractory cruci-

ble (Figure 12). By 1374, the Hindus had recognized that zinc was a new metal, and a limited amount of commercial zinc pro-duction was underway.From India, zinc manufacture moved to China where it developed as an industry to supply the needs of brass manufacture (Fig-ure 13). The Chinese apparently learned about zinc production sometime around 1600 AD., and from China zinc production became known in Europe about a century and half later. The Chinese also prepared another alloy which looked like silver but did not contain silver; instead, it contained copper. They called it pai-thung, i.e., white copper. It was imported to Europe in small quantities in the early 1700s. Much later, it was found out that this alloy contained a new metal that was called nickel.

Metals of the eighteenth century

In the eighteenth century, mineralogists, travellers, and analysts played an impor-tant role in the discovery of new metals. Mineral specimens from different localities were continuously supplied to laboratories where they were analyzed. It was a hobby of monarchs and wealthy people to collect minerals (Figure 14). This activity resulted in the discovery of cobalt, nickel, manga-nese, molybdenum, chromium, tellurium, and uranium (Table 1). Famous analyst of this period was Martin Heinrich Klaproth (1743-1817) (Figure 15) who discovered

Fig. 11: Antonio de Ulloa (1716-1795)

Fig. 12: Schematic representation of the Indian method for producing zinc

Fig. 13: Chinese method for producing zinc

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uranium. Beside the blowpipe which was a useful analytical tool for chemists, new reagents were discovered which were use-ful in isolating new metals. Also, the fall of the phlogiston theory contributed to the better understanding of the smelting proc-ess the main metallurgical operation.

Blowpipe

The blowpipe (Figure 16) was so essential for chemical analysis in the eighteenth cen-tury. With its help the qualitative composi-tion of most minerals was ascertained and the metals were discovered. The blowpipe is essentially a narrow tube with which air can be blown into the flame. By mixing suitable fluxes with the sample and using

an oxidizing or reducing flame, the min-eral samples were fused and from the color and appearance of the fused material it was possible to draw conclusions regarding its composition. This useful tool was aban-doned only after the invention of spectral analysis in the middle of the nineteenth century.

Discovery of hydrogen

Hydrogen discovered by Henry Cavend-ish (1731-1810) in 1766 was responsible for the isolation of pure metallic tung-sten by the Swedish chemist Jons Jakob Berzelius (1779-1848) (Figure 17) around 1783. Although hydrogen is a more pow-erful reducing agent than hot carbon, yet it failed to liberate the alkali metals, the alkaline earth metals, and aluminum from their oxides.

Discovery of chlorine

Chlorine discovered by the Swedish chem-ist Karl Wilhelm Scheele (1742-1786) in

1774 was used to convert oxides to chlorides from which metals could be obtained by reduction when the oxides resisted reduc-tion to metals. For example, niobium, zir-conium, vanadium were first prepared by reduction of chlorides when it was not pos-sible to reduce the oxides.

Fig. 14: Emperor Franz I (1708-1765) of Austria studies minerals at the Museum of Natural History in Vienna

Fig. 15: Martin Heinrich Klaproth (1743-1817)

Fig. 17: Jons Jakob Berzelius (1779-1848)discovered cerium, selenium, and thorium

Fig. 16: The blowpipe

Tab. 1: Metals discovered in the eighteenth century

Year Metal Discoverer Remarks1735 Cobalt Brandt Discovered in Sweden1741 Platinum Wood Metal from South America 1745 Boron Bergman Metal from the East. Isolated in 1808 by Gay-Luss-

ac, Thénard, and Davy1746 Zinc Marggraff Metal from the East1751 Nickel Cronstedt Discovered in Sweden1753 Bismuth Geoffrey Metalloid of the alchemists1774 Manganese Ghan Discovered in Sweden1781 Molybdenum Hjelm Discovered in Sweden1782 Tellurium Müller von

R e i c h e n -stein

Isolated by Müller von Reichenstein but not named. Named in 1798 by Klaproth

1783 Tungsten Elhujar brothers

Discovered in Spain

1789 Uranium Klaproth Klaproth believed that he prepared uranium metal when he reduced U308 with carbon. In fact he obtained only a lower oxide (UO2). The metal was isolated by Peligot in 1841 by the reduction of UCl4 with potassium

1789 Zirconium Klaproth Isolated by Berzelius in 1824 by the reduction of the fluoride with sodium

1791 Titanium Gregor Isolated by Berzelius in 1824 (impure metal), Nilson and Pettersson in 1887 (95 % pure), and by Hunter in 1910 (99.9 % pure).

1794 Yttrium Gadolin Discovered in Sweden1797 Beryllium Vauquelin Isolated by Wöhler and Bussy in 1828 by the reduc-

tion of the fluoride with sodium.1797 Chromium Vauquelin Isolated by Wöhler in 1859 by reducing molten

chromium chloride with zinc

Metals Through the Ages,Their Discovery and lsolationPat 2Habash. F ( l l

Seven melals were known lo lhe ancient people: gold, silver, copper, iron, morcury,lead, and tin. In the Middle Agos lho motalloids arsonic, anlimony, and bismutftwere added. Plalinum was later brought from South Amedca lhen zinc and b0r0nbocsmg known lrom lhe East. lt was only in the eighteenth century lhat mineralo-giab, travellers, and analysls supplled mlneral speclmens ftom dlfierenl localltiesto laboratodes where they lvere analyzed and this resulted inlhe discovery of ura-nium, zirconlum, yttrlun, berylllum, and chJomium, In lhe nineteenth century hebulk 0f metals became known mainly due io Swodish chomists, In tie tvJontielhcenlurylhevery rare remaining melalsi ftenium afld hafnium were discovercd andlsolated.In lhe meanlimo molals thatd0 notoccur in nalurc or occuronly in infini-tasimal quanlilios: piolacllnlum, lechnellum, tranciurn, promelhlum, and lhe lrans-uranlum molals bocamo known and woao isolatod. Roa8ons bohind thg discovgryaro analyz6d,

Flg, l9r Bobert Bunsen {1811 -1899)

ratories (Figure 20). This burnerpermitt€dhigher temperaiure to be achieved in thelaboratory when conducting a test. Beforethis burner the flame ofa candle or fromalcoholwasused.TheBunsenburner f l amepermitted perfonning the flametests (Fig-

ure2l) and latcr sp€ctroscopic anallsis.

Melals ol lhe nineteolh contuly

ln the l9th centurytheb{lkofmetals werediscovered (Table 2). This was a result oflhe discovery of electric cuaent and thcdev€lopment in analytical chemhtry and

The dlscovery ol elocltlc curront

At thc very beginni.g of the century, tbeItalian scientist Ale$andro Volta 1U451827) discovered electric current and thisproved to be a v€ry inportant toolfor m€t'allurgisls. Th€ newly invent€d Volta cellwas for the first time used by the Britishchemist Humphry Davy (1778-1829) (Iig-

ure l8) !o discove. new metals. Hejoineda large number ofth€se cells in seri€s, andthus was able to get . large current. Hedecomposed solid polash just moistenedto conduct cu(ent; he noticed that something burned brightly at th€ cathode.That

Fig. '18: Davy using Volta cells to l$lale so-diun and oolasslum

waspot.$iunmetal, which beingstronglyreactive, bumed in air. ln the sam€ way,he electrolyzed soda asb and demonstratedthatsodium metalcan be l iberated.The work of Davy and oth€rs opened anentirely new area in metallurgy, thouSh thefdct was nol recognized at that ti e. The'intense diificulties to b€ overcome whenremovihg the oxygen i-rcm $rch oxides asthose of potassnrn, sodirm, brriuh, calcium, ind m.gnesium clerrly suggestedthat the ilkaline metils themselves mightbe used to exlract thc oxygen fron otheroxides that pfove difficult to spln. Ahminum oxide was so ieshtant to allhedrodsofdecomposition that it was considered atone tim€ to be an elem€nt,lt wds lhe Dan-ish s.ientist Christian Oersted (1777 l85l)who in 1852 react€d aluminuft chloridewith potasium amalg.n from whichminute pa.ticles of aluminuered by distilling off the mercury. Themethodwas laterapplied to other chlo.ides

Flame lesls

It was Robert Bunren (1811-1899) (Iigure

19) at the Unive6ity of HeideLberg, whoaved the way for the great discoveries inthe niDeteenth centurywith bis inventionof th€ blrner in 1852 that caties his nameand is found today in nost chemical labo

Flg.20i Bunsen bumer

Thc dlscovcry ol th6 speclroscope

In the secoDd hallof the nineteenth centurythe spectroscope {Figure 22)was inventedby the Gcrman chemist Bunsen and thephysicht Kircbhoflin 18s9. Thh led to thediscovery of ibur new metals in theperiod1850 l8s3,namelycesiuh,rubidium,thallium, and indium.'lhe spsctroscope grad-ually displdced the blowpipe in chemicalanalysis. AD example of emissioD spectrais sho{n in Figure 23.

Fig. 21: Examples of colourcd llames inllame tesls

1801 holated by Blomstrand jn 1864 by reduc'tion ofNbcl. rvith H. and by Moissan inl90l by carbon reduction of Nb.o. in an

18021801 DG.overed in lngland

Discover€d in England

1807 Davy Dr\covered In FnShnd

1808Thenard, Davy

Dr\coveled rn Franceand Enshnd

Davy

Da!v

Davv

DNI

l8 l4 lsolated bv HrlleblJnd aDd Norlon rn 1895

l8 l7 L i th iuDl lsolated by D.vy in minuteamounh, butin lure form bv Arfwedson

1823 Si l iconta2718281830 koiated by Roscoe in 1869 by H, reduction

ofVCl: Prepa red by Marden and Rich inI927 Jpur i ty 99.9%lby reduct ion of the

1839t84l

18441860

l 86 l

Drcovcrcd !r EnulinJ

l86 l

t8751878t879

18801885

1886

18961898 holated byMne. Curie and Debierne in

t9t0Curie lsolat€d by Mme. Curie and Debierne in

t9 l0

1899 t so la ted b ! CE5e l in 1902

Tab.2r Mehls discovered and isolated in the nineteenti ceriury

Fig.22: A first sp€cfoscope

Flg, 23: Examples ol emission speclra: caFclum, stontium, and barlum

Foundation ol the alomic theoly

John Dalton (1766 1844)theEnglishteach-erolmaihematics and physics at New Col-lege nr Manchester showed in his book NewSystcm of Chemical Philosophy publishedin 18l0 howhis atomictheorycan beusedto explain the liwswhich govern chemical

lhe discov€ry oftfte Perlodlc Syslom

In 1869, the Rusian che'nist DimitryIvaDovitch Mendeleev (1834- 1907) (Figur€

24).rranged tbe elements with jn€reasing

atomicw€ight and discovered the PeriodicSystem leaving gaps in lhis Table for eletuents not yet discovered, and was able topredict tbeirproperties (Figure 25). Thisprediction helped the ch€mists at that timeto search for these elements. within twodecades the thfee metals gallium, scan-diuh, and gennanium were discov€red.The great similarity ir the chem ical prop'ertiesof the ra.e earlhsmade theirisolationa difficult task and th€ success in separaring them contributed to the knowledge of adozen new metals during this p€riod.

Fiq. 24: omiby lvanovitci MendelEov0834-1904

E6!a

|iT-TT-TT-TT--r]-T'T'II Il

Flg.25: llrendeleev's Pedodic Table of 1860 in modemform. Shaded areas werc prodlctod olemenl!, emplysoaces wera unknown

Melallolhermlc reaclions

examined the passage of electric current insolutions which led to the formulation ofthe laws of electrochemistry.

X-6ys and radioactivity

In 1895 x'rays were d iscovered by WilhelnConrad Roentgen {1845 1923) followedby the discovery ol radioactivity i! 1898by Antoine Henri Becquerei (1852 1908)which was responsible lor tbe discovery of

lolonium and radium shortly afterwardsby Mafie Cufie (1867-1914) (figure 26).A rar latef, Andra Debitrnc (1874-1949)( Figure 27), a .o '$o.kc. with Curie discovered and isolated actiriuD.

Fig.26r Plore Curio (1859-19{16) and llla eCurie (1867-19:14) making a me.surcmenlol a radloactlve subslance

Melals ol the lwentieth cenlury

llemcnts discovercd in thc 20th ccnturyarc thosc which arc vcry rdrc or do notoccur in nrtuie (T.b1e 3). Eldnents beyondplutonnun $e.c discordcd it the L.wrence Rrdi.tion Liboritory, UDivesity ofCililbmir frob 1944 lo L96l by Seaborg,McMi l lan, and Ghiorso:I 1944, amer ic iun dndcur iu l l ]

Chemists of the early nineteenth centurlused the alkali metals to libefate nretalsfrom their compounds -- a reaction thatbe.ame known as metallothermic rea-tion. The Swedish chemist ldns takobBerzeliN (1779 1848) isolated zirconiu'nrnd titanium in 1824 for the first timeby this method. The method was used in1850s by the lrench chemist HeDri Saint-Clane Deville (1818-1881) vho producedthe fi|st alominuh on indrstrial scale byheating AlCl, N.Clwith metallic sodiun.once aluminum became available itr largequantiti€s, it was aho used to liberate metals irom theif compounds.

The industiial producllon olaluminun

A great technological advancc was lhcinvention olthe dynamo in the 1870t tlulmade available electricity ir bulk whichencouraged the expansion of electrolyticcopper refining to supply the pure copperneeded for thc electrical indust.y. Anotherinpona.t applic.lion ofelectricity was inthe cl€ctrolytic production of rluhinum.once aluminum was available inexpen-sively, it was used for r€ducingotheroxidcsto metak. Thus, chromium and manga-nesewere prepared a fewyea6laterby this

Chemlcal cllects ol eleclrlc crrrent

Shortly .fter the discovery of the vol-taic pile, William Nicholson 0753 lsls)in England demonstrat€d th€ chemicaleffech oftbepile. He found that hydrogenand oxygen were evolved at the surface ofgold and platinum wires ifthey we.e con-nected with the terminals of a pile anddipped in water From this time on thenature of electriciry became an intensivetopic ofresearch simulta.eoudy by physicists and chemists. The physicists examining the pa$age ofelectricitl in gases andthey discovered the electron. The cbemists

Fig, 27: Andre Debldne ('l87+1949)

I 1949, berkeliunI I950, cr l i lbrn iumI 1952, e imtein iumI I956, nobel iunl

Developmenl of radiochemistry

Rad iochem isls played an inrporlant role inseparating the individual radioelements,thc i f ideot i f ica l idr , nnd thc i rarrangementin series, New mclhods of deasuremenissuch.s the CeiSer cou nter a nd theBaDrnascintill0tion counter replaced th€ gold leatel€ctroscope. Radirtions 1.on radioactivesubstances were identified rs alpha, beta,and grnmd. As. re$'lt two very rare ra<iioac tive nreta lsr prot!ct in iu m and franciu mwere d iscovered. Irrotactin ium was discov-ercd i l r r9r7-r8 by ot ro Hahn 0879,1968)and L iseMei tner (1878 1968) (F igure28) in

?

1907

T9T7 Isolated byvon Grosse in 1934.

t92l Isolated blvan Arkeland de Boer iD1925

t924.nd Berg

Discovered ir Cermany

t937 By bombardment ofmolybdenum witlld parliclesilaleron found in uraniuh

1939

1940,1961

r945

Tab.3r Metals discovered in lie lwenlielh cenlury

Fig.2gr otlo Hahn (1873-1968) and Lisetileihfi (1878-1968)

Gernlany the new element was part ofthedccay ch.in of uranium-235.lranciun wrs discovered in l9l9 at Curielnstitute ir P.ris, France by Margucrite

not continuous but occurs in small parcels. This allowed tbe understanding ofthe movement ofelectroDs in the atom bINiels Bohr (18851962), the hypothesis ofthe formation of electron $helh, and theexplanation oi emission spectra-

Electlonic slluclule ot rarc eadhs

Lr 1922 Bohr elucidated tbe ele.t.oni.structure of thc rarc carths (Table 4).The 14 rare earth elencnts were ideniified as "inner transition metak" and wereassigned r spe.irl phce in the PeriodicT.ble th.t becirne kDowD as lanthanideslIn this group thc tro oltermosr elect ronicshells are fillcd with the s.ne .!mber ofe lect rons, and i t is in lheth i rd shel l th i t thenumber of clcctrcnr is in.re.sed grudually.This explained lhe close similarily ofthencmbcrs of thi! group in rheir chehicalb€havioM. Bohr concluded that element72 vhich occu6 after lutetium must beterr i -v i len l rathc. th .n t r i ra l .n t and muslb. l ln lg to thc z i rconium hmi ly .Dd Dot lherare e.rths. He.dvised his co-workers inhis labor.tory tosearch lbr thiselement jn

X-ray analysis

X rdy+ie. t run.nr lys is by HeDryMoseley(1887'1915) in l9 l4 lcd k) lhc d iscovery oflwo n lc ta lsr haln i t rnr rnd rhenium.

Tab, 4: Elecfonlc stucturs 0t lanlhanldes, Al lhallime element 6l was not yet dlscovercd

I In i923, Dirk Coster (1889-19s0) (Iig-trre 3l) and Georg von Hevesy (18851966) (Fjgure 32) in Bohr: Institute inCopenhagen discovered element 72 ina Norwegian zircon and later in all thezi.conium min€rals and aU the com-mercial zirconium pr€paraiions theynrvestigated. This metal was namedhafrium for the cityofcopenhagen.

I ID l925ldaTacke (1896-1978) andWal-ter Noddack (1893-1962) (Iigure 33) ofthe Physico-Technical T€stjng Offic€in Berlin In lune 192s, witb the h€lpofOtto Berg, an X-rayspecialht at Sie'menlHalske identified in a Norwegiancolumbite a new €lement which theycal led.heniun in honour of th€ RiverRhein.

oiscovery of tho noutron

james chadwick (1891-1974) in Cam-bridge in 1932 explained the experim€ntsof Friddric joliot (1900-1958) and IraneCurie (1897 1957) in P.ris by supposingrliat alpha particleswer€ knocking neutralparticles out of the nuclei of the b€ryl-lium atom and that these neutral particlcs w€re in tur. knocking p.oions out ofthe p.ruffin. In this way the neutron was

l{ouiron capture

In 1934, Enrico Fermi ( 1901- 1954) in Romediscovered that neutrons may be capturedby atoms aod thatthe fiequencyofcaptureincreases when they a.e slowed down bypassing them through a hydrogen lichmaterial such as paraffin or water. He1\'as thus able to produce atoms ofhigheratomic weights than thosebombarded. Forexample, on bonbarding cobalt with n€u'tro.s he was able to producenickel. When,however he and his coworkers bombardeduranium with neukons, they obtainedmore than one radioactive product. lollowing the same line of thought as in theirprevious experiments they sugg€sted thatone of these pioducts was formed by neutron capture, i.e,, that it was a trans-urani-un element or element number 93. Iermi

Flg,29 add 3): Marguofile Perey (1909-1975) (lefl) and Georyes Uftain (1872-19:A)

Perey (1909-1975) ( I igure 29) l iom wbi .bthc clenrent trkes its D.De. lt wds discov-ered during the pMilicrtioD of d sdnrPleoiact in iuD 227. I t is ext remely rarc, v i thtrace imotrnts lbund in uranium rnd tho-rium ores, where the isotope h0nciuF223cootinually forns ind decays.

Tho discovory ot luietium

LutetiuD,elcntenLTl, wasdiscovered specboscopicxlly in 1907 by the lrench chcn].is tCeorges Urbain (1872 1938) (F igt r re30)

who Damed it atter Luliathc Roman ndmeofthe place where Pa fis was founded. lt Nasidentified by Bob. as a rare earth and lotas a member of GrouP lV

ouartun theory

The quantum theoryryMax Plan.k(18581947) is based on the principle thatenergylike matter js aLso composed of nrinutequantities called quanta, i.e., energy is

Flg.3l and 3,2: Dirk Coster (1883-1350)(10fi) and Georg von Hevesy (1885-1366)

Fig.33: lda Noddack lbom Tackel (1836-1978) and Waller Noddack (1&9&1962)

cles, the nuclear leactions that take pla€einvolve the emission ofan electron, a proton, or a helium nucleus and the mass ofthe bombarded atom suffers little change.when, however neutrons are used, newtypes of nuclear reaction should take placethat are completely different from those

Discovery of uraniun lissiorl

Fermit experiments were repeated byOtto Hahn (1879-1968)and his coworkersin Derlin. Th€y confirmed Fermi's conclu'sions and published a series otpapers onextensive radiochemical s€paratio.s ofthe so-called trans-uraniutu €lements.The results, however, b€came so contradictory that after fiv€ years of intensiveresearch and €xlensive publication theconcept of trans-uranium €lements hadto be abandoned. Hahn then announcedin January 1939 the definite formation ofbarium during the bombardm€nt ofura-nium and start€d speculating about themechanism ofits formation. Hahn couldnot accept the new idea thatthe uraniumatom was split into rwo fragments. Itwas Lise Meihrer ir Sweden who finallyexplained the results of the work as fis'sion, a f-ew motrthslft€rshe was forced toleave G€rmany in 1939.

Cyclotron

Th€ cyclot.on was invented by Ernest O.Lawrence (1901'1958) (Figure 35) of the

University of California, Berkeley, whereit was first operated in 1932. Byits meanstechnetium and the tlans uranium metais

lechnetiun

In i937 the Italian physicists Enilio Segrd

n9.34: Eka-fteniun accordlng to F.mi,l9:14

putthe newelement under.henium in thePeriodic Table and called it eka{henium(Figure34).Iermis papernatumllyattracted the atten-tion of Ida Noddack the discoverer of rhenium becaos€ i! d€alt with another elenentin the manganes€ gfoup. Soon afterward,sh€ published a paper which showed thatIermit experimental evidence was incomplete. She was critical of his conclusions,sayingthat all elements in the Periodic Sys-tem would haveto beeliminat€dbefor€onecouldclaim to have found a trans-uranium€lement. She went further and suggest€dthatr "when heavy nuclei are bombardedby neutrons, it would be reasonable to conceive that they break down into numeFous large fragments which are hotoPes ofknown elements but are not n€ighbounofthe bombarded elemenls fTranslation by

Her argumentwas as follows:wh€n atomsar€ bombafded by protons or alpha parti-

Flg.38.nd 37: Emlllo Sogrd (1906-1S)(b$ and Glenn T,Soaboru (tSlz-lSS)

(190s1989) (F igure36)andhirco 'worker

C. Perrier announced the d€tection oftheelement with atomic number 43 in tr.ceamounts in a molybdenum target whichhas been bombarded in the cyclotron forseveral months with a strong deuteronbeam. They called this new element tech-netium derivingth€ name from th€ Greek

Trans-uranlum molals

After elucidating the electronic structureof the trans-ufanium (Table 5) whichres€mbled that ofthe Ianthan ides, Seaborg(1912-199e) (Figu.e 37) proposed a secondle.ies of inner transilio! metals simil.rto the lanthanides that b€came knownas "actinides". He changed the PeriodicTable of l94s (ligure 38). Thus, uraniumwas r€moved from Group VI to becomea member ofthis new group as shown inFigure 39.

Promolhlum

The existence of a rare ea.th elementbetween neodyniun and samarium waspredicted by B.unauer This was con-tuned in l9l4 by Henry Moseley who,having measured the atomic nunbe.s ofallthe elements thenknown, found therewas no element lvith atomic number 5r.This element was discove.ed by Gl€nd'enin, Marinsky. and Coryell in 1945 atOak Ridge National Labor.tory in ura-nium fission products ard named "pro'

methium , Promethiun does not occur

Fig. 35: Emesl 0. Law€nce (1$1-1s8) lriglli] standing nsxl i0 lh6 cldolron

'ET;;TMI;I*I;I;[;T'T*T *I;EN

Fl0,38: Ihe Pedodic Table ol19{5

Fl0. {} Summary of ft8 dl8oovory ol mohls

Summaly

Figufe 44 Sives a summary ofthe dis€ov-eryof metals. Metalloidsknown durinStheAge ofAlch€my, platina from South Amer-

ica, and metals from the East are combined

in one period: Medieval m€lals. The Ii8-

u.e shows lhatthe metalsdiscovered inthe

19th c€ntury because of tbe discovery ofthe sp€ctroscope and the Periodic Table:I Specros.ope: cesium, rubidium, thal'

I PeriodicTable: gallium, scandium, ard

ln the 20th centlrry it was the discov-

ery of X-ray analysis, the new tools inradiochemistry, and the cyclotron thatled to the discovery of the last remainitrg

r X ray analysis: hafniun andrhenium

I N€w tools in radiochemist.y: francium

I Cyclotron: technetium and the trans-

Suggostod rcadln0s- L. Ancheson, A History ofMetals, 2 volunes,

Inte$cience. New York 1960- F. Hrbashi, edno!, A Hntory of.r,telallulsy,

MetallurE'e Err.ctive Queba., Quabec Citi,l99a: d,siribut.d by La€l UnLve6ity Book'

- F. H.bashi, Readinss in Hhtolical Metal-lurs. Volume r - Chme'nq Technoloay inlrir;dre Metallursy. Mdt;llursr lxliac

Flg. 3s Pedodic Ta!16 aflor 19{li incorDomling lho acfnldos

Tab.5: Eloctlr o ltuctnb 0l t|m3-onnlum

tik QnAbec, Qu{b.c City 2006r dlstribni.dbJ.LNal Univ{sity Boolctor.. vww.zon..

- M.E. Weeks. Dnco.

of th. Elements, 6lh.dition, lournal ofchimlc.l Edocation, E*-

(1) Fathi HabashL Departnent ol MininS,Metallutgi.oL, oM Materiak Engineering, Ldrol Ufive5ity, Quabec Citr,

rtEr^, t I Aa laft^ nd l ltDilE S'13 :