• Vo sredinata na 19 vek, Rusija ja razvila nejzinata te{ka i oboena industrija. Potrebata za metali bila golema. Paralelno so industrijata, se razvivale i naukata i tehnologijata. 

  Mendeleev bil roden vo Tobolsk, Sibir. Vo 1850 godina se zapi{al na Fakultetot za fizika i matematika na Glavniot Pedago{kiInstitut vo Petrograd, kade zavr{il vo brilijanten uspeh vo 1855 godina.  Podocna  podu~uval na fakultetot vo Odesa, kade prodol`il da raboti na me|usebnata vrska me|u kristalnite formi i hemiskite smesi na supstancite. Osven negovite teoretski istra`uvawa, Mendeleev rabotel i na aplikacijata na naukata vo industrijata i ekonomijata. Potoa rabotel i na Univerzitetot vo Hajdelberg, kade prv sorabotuval so Robert Bunsen, pritoa gi izu~uval kapilarnite fenomeni i nepravilnosti, na gasovite i  pareite, od zakonot na idealen gas. Vo 1860 godina,  Mendeleev otkril koncept za kriti~nata temperatura kaj istite i ova go prezentiral na Prviot Internacionalen Kongres vo Karlsrue. Tamu Kanicarovite pogledi za atomskite masi, kaj nego  poseaa seme za konceptot na periodniot sistem.  

  Vo 1864 godina Dimitri Ivanovi~ Mendeleev stanal profesor na Tehnolo{kiot institut vo Petrograd. ^etiri godini podocna toj po~nal da predava tehnolo{ka hemija. Kako i sekoj profesor toj moral da odlu~i kako }e gi podgotvi svoite predavawa. No, negovata misija bila te{ka poradi neredot koj vladeel me|u elementite, koi dotoga{ bile pronajdeni. Moral nekeko da gi podredi. Moral da najde najjasen i najlogi~en na~in za prezentirawe na 60 dotoga{ poznati elementi. Sobral mnogu knigi. Voda~i mu bile Lavoazije i Bercelius. Bidej}i za negovite studentite nemalo pogoden u~ebnik po hemija, go napi{al " Principite na Hemijata" (1868 -1871), koj se pojavil vo osum ruski, tri angliski i nekolku francuski i germanski izdanija. Negovite predavawa bile tolku interesni {to studenti i od drugite grupi gi posetuvale. 

  Sistematiziranite idei od ovaa kniga go vodele Mendeleev do formulacijata na negoviot perioden zakon, vo mart 1869 godina. Spored ovoj zakon gi podredil elementite spored atomskite masi, a pritoa predvidel postoewe na mnogu elementi. 

  Vo narednite godini, Mendeleev go modificiral i usovr{il svojot zakon, koj  bil primen so golem skepticizam vo visokite nau~ni krugovi. Vo Rusija , vo toa vreme, nikoj od Akademicite ne ja razbiral goleminata na negovata rabota. Negovata nominacija za po~esen ~len na Ruskata Akademija bila ignorirana, iako javnoto mislewe bilo na negova strana. Vo edna prilika toj izjavil: " Jas sum sam, tolku sam ". 

  Otkako nau~nicite Pol Emili Lecog de Boisbadran, Lars Frederik Nilson i Klements Binkler gi otkrile elementite galium (1875), skandium (1879) i germanium (1886), koi bile predvideni od Mendeleev vo 1871 godina    periodniot zakon bil nasekade prifaten.  

.
 

3. Anegdota za nau~nikot Dejvi 

• Dejvi bil golem nau~nik - hemi~ar koj `iveel pri krajot na 18 vek. Rabotel na otkrivawe na alkalnite metali. Toj bil nau~nikot koj gi otkril kaliumot i natriumot. 

         Toj bil celosno posveten na svojata rabota, no nesakal da propu{ti niedna ve~era, zabava ili bal na koi bil pokanet. Rabotel od rano nautro, pa se dodeka ne primetel  deka e vreme da odi na zabava. 

         Na zabavite negovite prijateli zboruvale me|usebe: - "O, poglednete go Gospodin Dejvi, kolku brzo se zdebelil!!". Pri slednata poseta, tie bile za~udeni:  Dali primetivte kolku e sega slab?? Neli e toa ~udno??  

        Tajnata bila vo {to toj rabotel mnogu naporno na negovite pronajdoci, {to nemal vreme da se izmie i da ja presoble~e ne~istata obleka.  ^esto oblekuval ~isti i beli ko{uli vrz ne~istata obleka. Ponekoga{ na nego edna vrz druga imalo i po duzina ko{uli i zatoa izgledal debel. Koga kone~no }e imal vreme da se presle~e, povtorno bil slab. So ova gi za~uduval svoite prijateli.     

        Mo`ebi ova se samo {pekulacii, mo`ebi ne, Koj znae?? 

5. Vodorod

  

	Vodorodot ima hemiski simbol  H i elektronska konfiguracija  1s1. Toj e gas bez boja, vkus i miris. Vodorodot e element koj gradi najmnogu soedinenija od site elementi.

Vo pove}eto  negovi  soedinenija, vodorodot e svrzan so kovalentna vrska. Katjonot H⁺ isto taka ima hemiska va`nost bidej}i igra va`na uloga vo acido-baznite reakcii. Toj isto taka e silno reduktivno sredstvo.

Vo vselenata, vodorodot e najrasprostranet element. Vo zemjinata atmosfera ima mnogu malku sloboden vodorod, a najmnogu go ima vo svrzana sostojba:voda i skoro site organski soedinenija. Vodorodot najmnogu se dobiva od zemjiniot gas, vo koj ima najmogu metan.

Vodorodot e diatomski gas, ima najmala gustina od site gasovi pri obi~na temperatura i pritisok. Zapalliv e. Ova svojstvo se koristi vo labaratoriite kako brz test za prisustvo na vodorod (bidej}i dava mala eksplozija koga e vo smesa so koslorodot od vozduhot).

Vodorodot ima tri izotopi:     

- Protium - so atomski broj 1

- Deuterium - so atomski broj 2

- Tritium - so atomski broj 3

Nakrako ke dademe nekoi od hemiskite svojstva na vodorodot:

Toj se vrzuva so kovalentna vrska vo skoro site negovi soedinenija. Ova e taka bidej}i vodorodovata jonizaciona energija e golema. Isto taka H+ jonot e proton i e ekstremno mal, taka da ovie mali golemini davaat isklu~itelni golema polarizaciona mo}.

Katjonot H+ vo voda,  deluva kako silna Luisova kiselina bidej}i so vodata gradi hidron jon H3O+. Ovoj jon igra centralna uloga vo mehanizmite na acido-baznite reakcii.

Naj~est oksidacionen broj na vodorodot vo negovite soedinenija e  +1, na primer vo soedinenijata HCl, H2O, no vo soedinenijata koi sodr`at hidriden jon H- toj ima oksidacionen broj  –1.

Kontroliranata eksplozivna reakcija me|u vodorodot i kislorodot se koristi kako dvi`e~ka sila na vselenskite letala.

Vodorodot isto taka se koristi i za redukcija na azotot do amonijak vo Haber-Bo{oviot metod. Ova e va`en metod vo koj atmosverskiot azot se vnesuva vo sinxirot na ishrana.

Jonizaciona energija    1312 kJ mol-1 ; radius na H+ jon 10-15 m

6.  Kolku e golema Avogadrovata konstanta

 Avogadrovata konstanta e poznat i mnogu golem broj. 

Eden univerzitetski profesor sakal na svoite studenti da im demonstrira kolku e golema Avogadrovata konstanta. Za taa cel toj re{il da transportira eden mol pesok vo univerzitetskata gradina, no pri toa se soo~il so golem problem.      

Da vidime vo {to bil problemot:

-         Vo eden mol ima 6,022 × 10²³ ~esti~ki ili zaokru`eno okolu  10²⁴ ~esti~ki.

-        Vo eden kuben metar pesok, ako zrnata se zamislat kako kocki so strani 0,1 mm, }e ima (10⁴)³ ili 10¹² (ili 1000000000000) zrna pesok.    

-         10²⁴ zrna pesok koi se pripa|aat na eden mol pesok go imaat sledniot volumen: 

10²⁴ zrna / 10¹² zrna vo eden mol pesok = 10¹² m³

-         Ako pesokot se transportira so kamioni, a sekoj od niv mo`e da nosi 10 m³, za 10¹² m³ pesok e potrebno:

10¹² m³ pesok / 10 m³  za eden kamion  = 10¹¹ kamioni so pesok

        Profesorot  znael kolku pesok trebalo da se prenese vo gradinata. Ostanalo u{te da se presmeta za kolku vreme }e se prenese pesokot. Ako vo 24 ~asa, na sekoi 10 minuti pristignuva po eden kamion, kolku vreme }e e potrebno da se prenese eden mol pesok:   

Vo eden den }e pristignat 6 kamioni * 24 ~asa = 144 kamioni

144 kamioni * 365,25 dena/ godi{no =  52596 kamioni vo edna godina

-         Na kraj  

10¹¹ kamioni / 52596 kamioni za edna godina  = 1901285,27 godini ili

 19013 vekovi 

Sega e o~igledno zo{to eksperimentot nemo`el da se prezentira. Profesorot nemal vreme za da go prezentira eksperimentot.

Samoukiot {vedski hemi~ar Karl Vilijam [ele ( Karl Wilhelm Scheele) bil apotekarski pomo{nik. Vo slobodnoto vreme eksperimentiral so mnogu hemikalii. Iako nemal sistematski pristap kon ispituvaweto, toj napravil va`ni otkritija. Bil prviot koj go identifikuval i dobil kislorodot. Go otkril hlorot, go izoliral fosforot i manganot, a gi opi{al fotohemiskiot efekt koj go davaat nekolku soli na srebroto – proces koj bil eksploatiran 50 godini podocna so otkrivaweto na fotografijata. Rabotata na [ele bila pozna~ajna od onaa na mnogu toga{ poznati Angliski i Francuski hemi~ari, no poradi nedostatokot na  akademsko obrazovanie nemo`el da gi publikuva svoite otkritija i ne gi dobil priznanijata koi gi zaslu`uval.

Samoukiot hemi~ar, Karl Vilijam [ele, bil roden na 9-ti dekemvri 1742 godina. Izu~uvaweto na hemijata go zapo~nal dodeka bil po~etnik vo apoteka vo Geteborg na ~etirinaeset godi{na vozrast ( od 1757 - 1765). Od 1765 do 1774  rabotel kako farmacevt vo Malme, Stokholm i Upsla. Vo 1775 se preselil vo Koping kako sopstvenik na apteka. 

Toj ne bil obrazuvan no bil roden hemi~ar, nemal asistent, u~el sam, pravel primitivni aparaturi od predmeti od okolinata. Sakal da znae ,,od {to e se napraveno,,.  

 Vo po~etokot eksperimentiral so mnogu kiselini i bazi. Edna{ uspeal da napravi gas so miris na gor~kiv badem. Go pomirisal i vkusil gasot da ja ispita aromata. Toa ne e dozvoleno nikoj da go povtori, bidej}i gasot koj go dobil e  HCN - cijanovodorod koj e mnogu otroven. Iako otkril jak otrov, bil mnogu sre}en bidej}i bil prviot koj ja videl ovaa supstancija. Vo edna prilika toj rekol:

Istra`uva~ot e sre}en koga }e go najde toa {to go tra`i. 

 [ele imal pokana, od Fredrik Veliki da ima katedra po hemija do krajot na negoviot `ivot i pokana za pomala pozicija vo Anglija, no i dvete giodbil.   

[ele bil gri`liv i ploden hemi~ar. Bil prviot koj go identifikuval kalcium fosfatot kako komponenta na koskite i poka`al deka mle~nata kiselina e pri~ina {to mlekoto so stoewe se zakiseluva. Vo rabotata so minerali, gi otkril hlorot, manganot i fluorovodorodnata kiselina, silikon flurid. Isto taka gi prigotvil molibdenskata kiselina, arsenovata kiselina, arsenidot i bakar arsenid ([eleevo zeleno). Od rastitelni i `ivotinski proizvodi, izdvoil golem broj organski kiselini, kako {to e glicerol, acetaldehid i mnogu esteri. Go dobil i ispital sulfurovodorodot.

          Po devetnaeset godini istra`uva~ka rabota bil izbran kako po~esen ~len na [vedskata akademija, no sepak toj ostanal obi~en laborant.

            Negovata prerana smrt, pokraj  revmatizmot i gihtot, bila rezultat na nekolku slo`eni i komplicirani istra`uvawa. Umrel na 21 maj 1786 godina, na 44 godi{na vozrast.

 

  8.  Table of detection

Name (Latin name)	symbol	Physical qualities	Discovered by/in	Use for making:
Copper(Cuprum)	Cu	Red-metallic element	Prehistoric period	Coins, cooking utensils, vats and ornamental objects, sheathing the bottom of wooden ships
Gold (Aurum)	Au	Soft, dense, bright, yellow metallic element	Etruscan, Minoan, Assyriah, Egyptian period	Basis for international monetary transactions, coinage, jewellery, in the arts of gilding and lettering.
Carbon (Carbonium)	C	Crucial to the existence of living organism	/
Tin (Stanum)	Sn	/	Ancient Egyptian	Protective coating for copper vessles, production of bronze, aerospace industry, ingrediant in some insecticides
Iron (Ferrum)	Fe	Magnetic, malleable, silvery-white, metallic element	About 4000 b.c. found in Egypt	Wrought iron, cast iron, steel, galvanized sheet metal and of electromagnets,medicine (anaemia)
Silver (Argentum)	Ag	White, lustrous metallic element that conducts heat and electricity	Before 2500 b.c. in Asia Minor	Jewellery, tableware, coins, mirrors, electronic components, medicine(antiseptics and bactericides), photographic plates.
Lead (Plumbum)	Pb	Dense, bluish-grey, metallic element, one of the first known element.	Romans empire	Storage batteries, sheathing electric cables, linig pipes, tanks, X-ray apparatus, protective shielding for radioactive material.
Mercury (Hydrargyrum)	Hg	Shining, mobile liquid, silvery-white, metallic element that is a free-flowing at room temperature	Antoine Laurent Lavoisier- (In his experiment of the composition of air.)	Thermometers, vacuum pumps, barometers, electric rectifiers and switches, as a source of ultraviolet rays, for sterilizing wather, instead of steam in boilers.
Sulphur (Sulphur)	S	Tasteless, odourless, light yellow,            non-metallic element	Prehistoric times	Manufacture of sulphur compounds, sulpha drugs, many skin ointments, matches, vulcanized rubber, dyes, gun powder.
Antimony (Stibium)	Sb	Bluish-white, brittle, semimetallic element	Basil Valentine (German Alchemic)-1450	Safety matches, vulcanized rubber, glass, porcelain.
Bismuth	Bi	Rare metalic element that has a pinkish tinge	Ancient time	For measuring the strength of magnetic fields, fluoroscopy (he is opaque to X-rays)
Arsenic	As	Extremely poisonous semimetallic element	Ancient time	Manufacture of glass, military poison gases, sulpha drugs, antibiotics, insecticide, laser materials, paints.
Zink	Zn	Bluish-white metalic element that has many industrial applications	Andreas Sigismund Marggraf (German chemist) - 1746	Galvanizer, ingredient of various alloys, especially brass, plates for dry electric cells, die castings.
Nitrogen (Nitrogenium)	N	Gaseous element that makes up the largest portion of the Earth`s atmosphere	Daniel Ruherford (British doctor) - 1772	To synthesize ammonia, fertilizers, laughing gas (N2O) ; anaesthetic for some types of surgery.
Hydrogen (Hydrogenium)	H	Reactive, colourless, odourless and tasteless gaseous element	Henry Cavendish (British chemist) - 1766	As catalyst to form ammonia, hydrogen sulphide, hudrogen clorine, water.
Oxyen (Oxygenium)	O	Colourless, odourless, tasteless, slightly magnetic gaseous element	Joseph Pristley (British chemist) - 1774	In high-temperature welding torches, open-hearth furnaces ; for steel manufacture, liquid propellant for guided missles and rockets
Chlorine (Chlorum)	Cl	Greenish-yellow       non-metallic element	Carl Wilhelm Scheele (Swedish chemist)- 1774	For bleaching paper pulp, preparing bromine ; as a poison gas (in World war II)
Cobalt	Co	Silvery-white magnetic metallic element	George Brandt (Swedish chemist) - 1735	For making alloys ; in industry ; as aircraft gas turbine engines ; for permanent engines ; in ceramics, paint driers ; as a catalyst
Platinum	Pt	Relatively rare, chemically inert metallic element, more valuable than gold	Ancient Geece and Rome	Contact points in electrical apparatus, measuring high temperatures;as a catalyst,into lewellery;
Nickel	Ni	Silvery-white magnetic metallic element	Baron Axel Frederic Gronstedit (Swedish chemist) - 1751	As a protective and ornamental coating for metals ; as a catalyst, chiefly in the form of alloys ; for car parts ; for armour plate
Manganese	Mn	Silvery-white, brittle metallic element	Carl Wilhelm Scheele (Swedish chemist) -1774	Principally in the form of alloys ; as a deoxidizer ; for propeller blades on boats and torpedoes ; in the form of wire for accurate electrical measurements.
Wolfram (Tungsten – new name)	W	Metallic element that has the highest melting point of any metal	Carl Wilhelm Scheele (Swedish chemist)- 1783	As flaments in incadescent lamps ; as wires in electrical furnaces ; in manufacture of spark plugs, electrical contact points, and as a target in     X-rays tubes
Molybdenum	Mo	Metallic element that has qualities similar to those of Chromium	Carl Wilhelm Scheele (Swedish chemist)- 1778	Chiefly in alloying steel ; in electron tubes ; as a lubricant in enviroments requiring high temperatures
Uranium	U	Chemically reactive radioactive metallic element	Martin Heinrich Klaproth (German chemist) - 1789	As main fuel in nuclear reactors, nuclearic weapons, nuclear power
Titanium	Ti	Silvery-white metallic element	William Gregor (British clergyman) - 1791	For making strong alloys ; in aircraft for fire walls, missles and space capsules ; in heat excangers in desalination plants, paints, lacquers, plastics, paper, textiles, rubber.
Chromium	Cr	Grey metallic element that can take on a high polish	Louis Nicolas Vouguelin (French chemist) - 1797	To form alloys ; as high-speed metal-cutting tools ; as body trim on cars and other vehicles
Kalium (Potassium)	K	Chemically reactive, extremely soft metallic element	Sir Humphry Davy (British chemist) - 1807	In photoelectric cells ; in lithigraphy, as a sedative in medicine ; in matches, fireworks, explosives
Sodium	Na	Highly reactive, silvery-white, extremely soft metallic element	Sir Humphry Davy (British chemist) - 1807	As a cooling agent in nuclear reactors, manufacture of tetraethyl, lead, rayon, paper ; in oil refining, textile, rubber, photography (fixing)
Magnesium	Mg	Silvery-white metallic element that is relatively unreactive	Sir Humphry Davy (British chemist) - 1808	As dressing and filler for cotton and woollen fabrics, paper manufacture, cements, ceramics, medicine (laxative "milk of magnesia")
Strontium	Sr	Chemically reactive, malleable, ductile metallic element	Sir Humphry Davy (British chemist) - 1808	In the manufacture of fireworks and flares ; in recovering sugar from sugar-beet molasses, detection of bone cancer
Barium	Ba	Soft, silvery, highly reactive element	Sir Humphry Davy (British chemist) - 1808	In coating electrical conductors ; in wlwctronic apparatus and in car ignition systems ; in rubber products, paint, linoleum, as rat poison
Calcium	Ca	Reactive,silvery-white metallic element	Sir Humphry Davy (British chemist) - 1808	To an increasing extend as a deoxidizer ; in storage batteries ; as sheating for lead-covered cable
Cerium	Ce	Soft, grey metallic element	Baron Jons Jakob Barzelius (Swedish chemists) - 1803	In the manufacture of glass, ceramics, arc-lamp electrodes, photoelectric cells
Selenium (Selenum)	Se	Semimetallic element	Baron Jons Jakob Barzelius (Swedish chemists) - 1817	To impart red colour to clear glass ; as a decolorizerof glass ; into vulcanized rubber
Silicon	Si	Semimetallic element that is the second most common element on Earth	Baron Jons Jakob Barzelius (Swedish chemists) - 1823	As a constituent of silicon-steel alloys ; in transistors and integral circuits ; in the manufacture of glass, enamels, cement, porcelain
Zirconium	Zr	Metallic element	Baron Jons Jakob Barzelius (Swedish chemists) - 1824	In the manufacture of glass, enamels, cement, porcelain ; in vacuum tubes, in heat exchanger, pump housing
Thorium	Th	Radioactive metallic element	Baron Jons Jakob Barzelius (Swedish chemists) - 1828	As a potential atomic-fuel, in magnesium allous ; as a stabilizing component of electronic tubes, light flaments
Caesium	Cs	White, soft, chemically reactive metallic element	Robert Wilhelm Bunsen (German chemist) and Gustav Robert Kirchoff (German physicist) - 1860	To remove residual oxygen from radio vacuum tubes ; in the photosensitive surface of the cathode of the photoelectric cells
Rubidium (Rubidus)	Ru	Chemically reactive metallic element	Robert Wilhelm Bunsen (German chemist) and Gustav Robert Kirchoff (German physicist) - 1860	In making catalysts and photoelectric cells ; in geologic age determination
Gallium	Ga	Metallic element that remains in the liquid state over a wider range of temperatures	Paul Emile Lecoq de Boisbaudram (French chemist) - 1875	To adventage in high-temperatures ; in rectifiers, transistors, photoconductors, laser, maser diodes
Helium            ( helios )	He	Inert, colorless, odorless, gaseous element	Pierre Jonssen (French astronomer) - 1868	In inert-gas arc welding for light metals ; in medicine to relieve suffers of respiratory difficulties ; to shrink blood-vessels malformation in the brain of patients
Argon	Ar	Inert gaseous element, that is the third most prevalent gas in the Earth`s atmosphere	Sir William Ramsay and Baron John William Strutt Rayleigh (British chemists) - 1894	In one type of neon lamp, electric-arc technology, gas lasers, arc-welding
Neon	Ne	Colorless, odorless, gaseous element	Sir William Ramsay and Morris Travers (British chemists) - 1898	In neon lamp of advertising displays ; as a refrigerant in cryogenics
Krypton (kryptos)	Kr	Colorless, odorless, gaseous element	Sir William Ramsay and Morris Travers (British chemists) - 1898	With Argon and Neon in incandescent bulbs ; in lighting airfields
Xenon	Xe	Colorless, odorless, gaseous element	Sir William Ramsay and Morris Travers (British chemists) - 1898	Principally in such lighting devices as high-speed phtographic tubes
Radium (radius)	Ra	Chemically reactive, silvery-white, radioactive, metallic element	Marie Currie and Pierre Curie (French chemists) - 1898	In the treatment of only a few kinds of cancer ; small amounts were used in the production of luminous paint
Polonium	Po	Rare, radioactive metallic element	Marie Currie(French chemist) - 1898	In nuclear research ; in devices that ionize the air to eliminate accumulation of electrostatic charges
Actinium	Ac	Radioactive, metallic element	Andre Louis Debierne (French chemist) - 1899	/
Protactinium	Pa	Radioactive, metallic element	Lise Meitner (Austrian-swedish physicist) and Otto Hahn (German physical chemist)- 1918	/

  

  9.  Discovery of the chemical elements

 When in the XIX century the necessity of initiation order among the chemical elements had been appeared, only half of the today`s known elements were familiar.

The first elements which human had known were those that can be meet free in the nature. The red colour of the Copper and the yellow colour of the Gold, and of course their metal glow atracted the attention of human in the neolit period.When he learned the features of metals and found the way to get them form their ores, human began to make objects from metals, which he had produced of bones, stone and wood. This is the metal age in the evolution of the humanity. Copper was first used, then Bronze, alloy of Copper and Tin, and then Iron. In the old age, Silver, Lead and Mercury, from metals and Carbon and Sulphur, from nonmetals, were also known beside Gold, Copper and Tin.

Middle age is period of alchemy. Alchemicst tried to get the philosophic stone, which would allow transemutation, converting of metals into gold, and to discover elixsir of youth, which would allow health and eternal youth. Certainly that alchemist didn`t succeed, but they also didn`t succeed to increase the number of elements. From this fewcentury age are known Bismuth, Antimony, Arsenic and Zink. Boyle, lomonosov, lavoisier, Dalton and others scientists of XVII and XVIII century, with their work enable chemistry to start developing as a science, and in the second half of XVIII and XIX century  chemistry developed, (theoretically and experimentally), as a real science. That certainly caused discovering of new elements. In the XVIII century were discovered gaseous elements Nitrogen, Hydrogen, Oxygen and Clorine, and metals Cobalt, Nickel, Manganese, Wolfram, Molybdenum, Uranium, Titanium and Chromium.

14 elements were discovered in the first decade of XIX century. Davy succeeded to isolate  6 elements: Kalium, Sodium, Magnesium, Strontium, Barium and Calcium, with electrolysis of different salt. Berthollet discovered  the Cerium, and later also Selenium, Silicon, Zirconium and Thorium. Besides this, Barcelius installed the chemical symbols for marking the chemical elements. He suggested as chemical symbol to take the first letter of the lattin name of elements, and if there are more elements which begin with the same letter, besides the first to be taken another letter of the name.This way of marking of chemical elements is adopted, and it applied today, so chemical symbols are short international signs of the chemical elements.

In 1930, 55 elements were known, what brought to necessity of installing order between them. Deberayner, Newlens and Meyer had tried in it, but only one gave the best classification of elements – Dmitry Ivanovich Mendeleyev. He subordinated the chemical elements according to their relative atomic masses, atomic weight, as it was called then, and in intermission he had discovered the periodity law of quality of elements. Mendeleyev left gaps, about the elements which hadn`t been discovered yet, what appeared right. With the quick developement of chemistry and physics at the end of  XIX and XX century, is was allowed to fill up the Periodical system.

Elements:Caesium, Rubidium, Gallium, noble gas Helium, had been discovered with spectroscopical metods, based on their characteristic spectars.Argon had been discovered before that, and later other noble gasses Neon, Krypton and Xenon.

In the period from 1983 to 1907 were discovered 14 elements with a lots of similar qualitis, Lantanoids, called rare land.

The discovery of radioactivity, brings discovery of new elements, based on this quality, such as Radium and Polonium.

In the XX century by artificial way were got elements which can`t be seen in the nature, such as all actinoides, exept Actinium, Torium, Protactinium and Uranium.

The names of elements aren`t systematic. They are given according to some quality of the element, according to some compounds in whose composition enter the element, according to the nature country of the scientist who had discovered the elements or according the name of some scientist. Thus the element Chlorine got the name, from some greek word "hloros" which means green, and Argon is greek word which means inert. Hydrogen is from the lattin word "hydrogenium" which means create wather. Polonium is called after Poland, and Gallium after Galia, the old name of France.

Mendelevium is called accord to Dimitri Ivanovic Mendeleev. It can be given answer of the question "how many elements have been known". But, how many elements are still unknown ? Maybe non in the 21 century this question will not be answered, but surely the number of unknown elements will be reduced. 109 elements up till now are known.

Menthor: Gecheska Gordana  Written by: Dinev Bojan

 

 

10.  Noble Metals

Historically, the noble metals I suppose were "noble" because you had to be a rich noble to afford to own any. It then took on the connotation of non-reactive because Cu, Ag, Au, Pt, and Pd are frequently found as metallic ores, rather than as oxides, sulfides or other compounds.

This whole concept has lost its meaning of "non-reactive" as modern chemistry and metallurgy have discovered other elements such as Ru, Ti, Ta, and others that are quite resistant to heat and chemical attack.

          To call metals "noble" is a classification somehow out-of-date... it means that in the activity series of metals they are placed after the hydrogen and then, do not react with acids to form hydrogen. These metals are in order: copper, silver, mercury, platinum and gold.  Noble also could mean they are beautiful, precious, and valuable and are used to make jewelers,  mostly silver, gold and platinum. And also can mean they are very difficult to be attacked or to react chemically...like the  other metals from the  platinum group.

          Either way, noble metals known to man today are: Ag, Au and the Platinum group (Os, Ir, Pt, Ru, Rh, Pd).

GOLD

The essentials
Name: gold  ;  Symbol: Au        Color: gold  ;  Standard state: solid at 298 K

Atomic number: 79 ;                   Classification: Metallic  ; 

Atomic weight: 196.96655        CAS Registry ID: 7440-57-5 ; 

Group number: 11 ;                     Group name: Coinage metal

Period number: 6 ;               Block: d-block

Description: Gold is usually alloyed in jewelers to give it more strength, and the term carat describes the amount of gold present (24 carats is pure gold). It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft. on a side. It is metallic, with a yellow color when in a mass, but when finely divided it may be black, ruby, or purple. It is the most malleable and ductile metal; 1 ounce (28 g) of gold can be beaten out to 300 square feet. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most reagents.

The most common gold compounds are auric chloride (AuCl₃) and chlorauric acid (HAuCl₄). A mixture of one part nitric acid with three of hydrochloric acid is called aqua regia (because it dissolved gold, the King of Metals). It is unaffected by air and most reagents. It is found free in nature and associated with quartz, pyrite and other minerals. Two thirds of the world's supply comes from South Africa, and 2/3 of USA production is from South Dakota and Nevada. Gold is found in sea water, but no effective economic process has been designed (yet) to extract it from this source.

Isolation: It would not normally be necessary to make gold in the laboratory as it is readily available commercially. The most romantic way to extract gold is by panning it out from a stream in some pleasant valley but most such sources are now depleted. Panning relies upon the density of gold (which is very high) being much greater than that of the sand and other particulates. It therefore settles to the bottom of the pan.

Today, more often than not, gold is extracted from ores. These ores often contain relatively little gold. Some of these processes cause environmental concern. The ore is crushed to a powder so as to expose the small gold particles. These are dissolved by treatment of the rock with cyanide solution in air. The result of this is a gold cyanide complex. Addition of zinc powder to the resulting solution precipitates out the gold.

4Au + 8NaCN + O₂ + 2H₂O ® 4Na[Au(CN)₂] + 4NaOH

2Na[Au(CN)₂] + Zn ® 2NaCN + Zn(CN)₂ + Au (s)

Historical information

Discovered by: Known since ancient times.

Discovered at: not known

Discovered when: no data

Origin of name: From the Anglo-Saxon word "gold" (the origin of the

symbol Au is the Latin word "aurum" meaning "gold")

Gold was known and highly valued from earliest times. Egyptian inscriptions dating back to 2600 B.C. describe gold and gold is mentioned several times in the Old Testament.         It is almost certain that the gold was the first metal that man met, because it can be found in native state unmixed with other metals or ores. Bright yellow color surely must have brought attention to prehistoric men but there is no evidence of when did this actually happen. Some of the earliest information about gold are old about 5 500 years. People from the stone age learnt to turn gold into jewelers and ornaments because of its beauty and color. There are dates about the use of gold by the Asirians in 2 470 year BC. Some time later, gold was used for coins along with copper and zinc.

          Today, gold is used for making jewelers, different medical prostheses, medals, plates and coins and ...  Probably gold is the most ideal metal for coins because of its characteristics. Coins from pure gold were made in England but later gold alloys, like electrum and crown gold, found greater use than gold itself.

          85% of the world production is used for jewelers, 6% in electronics, 4% for coinage, 2% in dentistry and 3% for different industrial applications.

          Summary- gold is used for:

·        coinage metal, standard for monetary systems in many countries

·        jeweler, decoration

·        dentistry

·        plating. It is used for coating space satellites, as it is a good IR
reflector and is inert.

• chlorauric acid (HAuCl₄) is used in photography for toning the silver image
  
• Disodium aurothiomalate is administered (intramuscular) as a treatment

for arthritis

• electronics
• photography for toning silver images
• 198Au is used for treating cancer and other conditions

 Interesting facts about gold:

• Gold is one of the world's most precious metals.
• All of the gold in the world could be compressed into an 18-yard cube,

which is about 1/10 the mass of the Washington Monument

• It is recorded that only 88,000 tons of gold have been taken from the

earth since recorded history, leaving far more yet to be discovered.

• A one-ounce gold nugget is more rare to find than a five-carat diamond.
• The amount of gold nuggets being found in the world is less than one

percent.

• Even though gold is rare, it is far easier to find than winning a major

state lottery.

• Because of its rarity, a gold nugget can be worth three to four times

the value of the gold it contains.

• An authentic gold nugget has long been considered a gemstone because of

its rarity and beauty.

• Gold is so heavy that one cubic foot of it weighs half a ton.
• Gold is six to seven times heavier than other materials that equal its

size.

• The largest gold nugget found in the U.S. weighed 195 pounds; it came

from California.

• Gold can be hammered so thin that sunlight can shine through it.
• A single ounce of gold can be drawn into a wire 60 miles long.
• Gold can be hammered into sheets so thin that a pile of them an inch

high would contain more than 200,000 separate sheets.

• In every cubic mile of sea water there is 25 tons of gold! That's a

total of about 10 billion tons of gold in the oceans; however, there's no

known way to economically recover it.

• Gold is considered one of the most important metals in jewelry making.
• Gold is so soft it is seldom used in its pure form.
• Jewelry that is marked 10K is made of 10 parts gold, and 14 parts other

metals.

• The hardness of pure gold (on moss scale) is 2-1/2 to 3; the melting

point is 2,063 degrees Fahrenheit, specific gravity is 19.32, and

tensile strength is 19,000psi.

• Gold can be transmitted from platinum by nuclear reaction. But, because

of the rarity of platinum, it is far too costly.

• The United States government banned private ownership of gold, which

lasted 41 years; then lifted it on December 31, 1974.

• Gold reached an all-time high price of $800 per ounce in 1980.

South Africa is the largest producing gold country in the world today

• An ounce of gold is based on troy weight--20 pennyweights or 480

grains. A pound of gold is 12 ounces, while most other non-precious metals

are based on the standard avoirdupois scale of 16 ounces to the pound,

and approximately 32 grams to the ounce.

• Gold is chemically liquefied and injected into the muscles of thousands

of rheumatoid arthritis victims in the U.S., and it is said that the

treatment is successful in seven out of ten cases.

• Gold is used in window glass and astronaut helmets to reflect infrared

rays while allowing sunlight to pass through, and at the same time

keeping it cool.

• Gold is inactive chemically and is not affected by air, heat, moisture

and ordinary solvents.

• The largest gold mine in the U.S. is the Home stake Mining Company in

Lead, South Dakota.

• This article was first published in the December, 1988 issue of Gold

and Treasure Hunter magazine Interesting...

• Gold has always been associated with wealth and power and for good reason
• Gold is valuable because it is scarce.
• largest nugget of near-pure gold discovered was found in Australia. It

produced 142 pounds of pure gold.

• scientists believe that there may be 70 million tons of gold in the

ocean - but how to get to it?

• the desire to produce gold from other less valuable metals resulted in

experiments conducted by people know as alchemists and the beginnings

of the science of chemistry.

Silver

The essentials

Name: silver                                                                  Standard state: solid at 298 K

Symbol: Ag                                                                   Color: silver

Atomic number: 47                                                       Classification: Metallic

Atomic weight: 107.8682 (2) g

CAS Registry ID: 7440-22-4

Group number: 11

Group name: Coinage metal

Period number: 5

Block: d-block 

Silver is somewhat rare and expensive, although not as expensive as gold. Slag dumps in Asia Minor and on islands in the Aegean Sea indicate that man learned to separate silver from lead as early as 3000 B.C. Pure silver has a brilliant white metallic luster. It is a little harder than gold and is very ductile and malleable. Pure silver has the highest electrical and thermal conductivity of all metals, and possesses the lowest contact resistance. Silver iodide, AgI, is (or was?) used for causing clouds to produce rain.

Silver is stable in pure air and water, but tarnishes when exposed to ozone, hydrogen sulphide, or air containing sulfur. It occurs in ores including argentite, lead, lead-zinc, copper and gold found in Mexico, Peru, and the USA.

 Isolation: Silver is readily available commercially so it is not normally necessary to prepare silver in the laboratory. However the formation of silver metal may be demonstrated in a satisfying reaction in which copper metal is dipped into a solution of silver nitrate, AgNO₃.

Cu(s) + 2 AgNO₃ (aq)  Cu(NO₃)₂ + 2 Ag (s)

The result is formation of often attractive silver crystals and a blue-green solution of copper nitrate. Industrially, silver is usually a byproduct of processes whose main object is the extraction of another metal such as copper, lead, and zinc. So called "anode slimes" from the electrolytic purification of copper contain silver and a somewhat involved process is finished by an electrolysis of a nitrate solution containing silver.

 Historical information

Discovered by: Known since ancient times

Discovered at: not known

Discovered when: no data

Origin of name: From the Anglo-Saxon word "siolfur" meaning "silver"

(the origin of the symbol Ag comes from the Latin word "argentums" meaning

"silver")

Silver has been known since ancient times. It is mentioned in Genesis.

Slag dumps in Asia Minor and on islands in the Aegean Sea indicate that

man learned to separate silver from lead as early as 3000 B.C.

          Silver was found in the tombs in Ur from about 3 000 years. Because it is too soft to be used in native state, silver is alloyed with other metals like copper.

Uses:

·        Sterling silver is used for jeweler, silverware, etc. where appearance is paramount. This alloy contains 92.5% silver, the remainder is copper or some other metal

• photography (AgBr) 28%
• dental alloys
• solder and brazing alloys
• electrical contacts 17%
• high capacity silver-zinc and silver-cadmium batteries

• silver paints are used for making printed circuits
• used in mirror production and may be deposited on glass or metals by

chemical deposition, electrode position, or by evaporation. When freshly deposited, it is the best reflector of visible light known, but it rapidly tarnishes and loses much of its reflectance the iodide is used to seeding clouds to produce rain the nitrate, (lunar caustic) is used extensively in photography coinage metal

• coins 3%
• jeweler 35%
• Industrial appliances

 Specimens

Silver has been mined for eons and has always been popular in jewelry and for coinage. Only in the past hundred years however, has the demand for silver been so great. The reason for this demand is the use of silver in the photography industry, which takes advantage of silver's reactivity to light. Native Silver is rare and much silver is produced from silver-bearing minerals such as porosity, pyrargyrite, galena, etc. Specimens of Native Silver usually consist of wires that are curved and intertwined together, making an inspiring mineralogical curiosity.

 PHYSICAL CHARACTERISTICS:

Color is silver white with exposed specimens tarnishing black.

Luster is metallic.

Transparency is opaque.

Crystal System is isometric; 4/m bar 3 2/m

Crystal Habits include massive and disseminated grains, wires and plates as the most common, whole individual crystals are extremely rare but when present are usually cubes, dodecahedrons and octahedrons. "Jack Frost" type crystal growth as shown on some specimens produces beautiful intricate structures. Wires can form coiled clusters that resemble rams horns.

Cleavage is absent.

Fracture is jagged.

Streak is silver white.

Hardness is 2.5-3.

Specific Gravity is variable according to purity 10-12 (well above average even for metallic minerals)

Associated Minerals are silver minerals such as acanthine and porosity, cobaltite, copper, zealots and quartz.

Other Characteristics: ductile, malleable and sectile, meaning it can be pounded into other shapes, stretched into a wire and cut into slices.

Notable Occurrences include Michigan and Arizona, USA; Cobalt, Ontario; Chile; and Germany.

Best Field Indicators are color, tarnish, ductility and crystal habit.

Facts on Silver

·        Silver is the most reflective metal, which means that it can be polished to "give back" as much light as hits it.

·        Silver is the best heat conductor of all metals. Its uses in solar panels and automobile rear window defoggers take advantage of this quality.

·        Silver alloys readily with gold and copper and is commonly combined with one or both for manufacture of dental fillings and fixtures, jewelry and silverware.

·        Silver has the capacity to join, or "wet", other metals at temperatures far below their melting points. It is for this reason that silver brazing alloys and solders are commonly used in tubing and electrical conduits for household appliances such as refrigerators and dishwashers.

·        Silver has a pure sweet acoustic resonance, better than any other metal, and is preferred by musicians for making high quality silver bells and musical instruments.

·        The atomic weight of silver is 107.870, and its atomic number is 47.

·        Silver melts at a temperature of 1761 degrees F. or 960 degrees C.

·        Silver has a specific gravity of 10.5. When melted silver can absorb

as much as 20 times its own volume of oxygen.

 ·        The film coating on mirror backings is a common "industrial" use of silver. Besides vanity uses, mirrors are important components in telescopes, microscopes and solar panels.

·        Sterling silver contains 92.5% silver and 7.5% copper. 14 karat gold consists of 53% gold, 25% silver and 22% copper.

·        Silver is not changed by moisture, dryness, alkalis, or vegetable oils, but sulfur will cause silver to turn black

Platinum
The essentials                   Name: platinum                             Standard state: solid at 298 K
Symbol: Pt                        Color: grayish white
Atomic number: 78            Classification: Metallic

Atomic weight: 195.078 (2)

CAS Registry ID: 7440-06-4

Group number: 10

Group name: Precious metal or platinum group metal

Period number: 6

Block: d-block 

Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. It has a coefficient of expansion almost equal to that of soda-lime-silica glass, and is therefore used to make sealed electrodes in glass systems.

The metal does not oxidize in air. It is insoluble in hydrochloric and nitric acid, but dissolves when they are mixed as aqua region, forming chloroplatinic acid (H2PtCl6), an important compound. It is corroded by halogens, cyanides, sulphur and alkalis. Hydrogen and oxygen gas mixtures explode in the presence of platinum wire.

 Isolation

It would not normally be necessary to make a sample of platinum in the laboratory as the metal is available commercially. The industrial extraction of platinum is complex as the metal occurs in ores mixed with other metals such as palladium and gold. Sometimes extraction of the precious metals such as platinum and palladium is the main focus of a particular industrial operation while in other cases it is a byproduct. The extraction is complex and only worthwhile since platinum is the basis of important catalysts in industry.

Preliminary treatment of the ore or base metal byproduct with aqua region (a mixture of hydrochloric acid, HCl, and nitric acid, HNO₃) gives a solution containing complexes of gold and palladium as well as H₂PtCl₆. The gold is removed from this solution as a precipitate by treatment with iron chloride (FeCl₂). The platinum is precipitated out as impure (NH₄)2PtCl₆ on treatment with NH₄Cl, leaving H₂PdCl₄ in solution. The (NH₄)2PtCl₆ is burned to leave an impure platinum sponge. This can be purified by redissolving in aqua region, removal of rhodium and iridium impurities by treatment of the solution with sodium bromide, and precipitation of pure (NH₄)2PtCl₆ by treatment with ammonium hydroxide, NH₄OH. This yields platinum metal by burning. 

Pure platinum is unknown of in nature as it usually is alloyed with other metals such as iron, copper, gold, nickel, iridium, palladium, rhodium, ruthenium and osmium. The presence of these other metals tends to lower the density of platinum from a pure metal specific gravity of 21.5 to as low as 14 and very rarely any higher than 19 in natural specimens. Few of these rarer metals form significant deposits on their own and thus platinum becomes the primary ore of many of these metals. The presence of iron can lead to a slight magnetism in platinum nuggets and is a common enough property to be considered diagnostic.

The element platinum is extremely scarce in most crystal rocks, barely seen as even a trace element in chemical analysis of these rocks. However platinum seems to be much more concentrated in the mantle and can be enriched through magmata segregation. Platinum's origin in the crust is from ultra-mafic igneous rocks and therefore platinum is associated with minerals common to these rocks such as chromite and olivine. Platinum's most common source however is from placer deposits.

Over the ages, the platinum became weathered out of the igneous rocks and were tumbled down streams and rivers where the extremely heavy grains and nuggets of platinum collect behind rocks and bends in the rivers and streams. These deposits, called placers, that form behind the rocks and bends are enriched in heavy grains as lighter material is carried further down stream. The heaviest grains are the nuggets of gold, platinum and/or other heavy minerals.

The metal platinum is a valuable metal that is gaining in importance. It is typically more expensive by weight than gold, mostly a product of its scarcity. Platinum is very non-reactive and for this reason it is used in chemical reactions as a catalyst. Metallic platinum can facilitate many chemical reactions without becoming altered in the process. It is also used in many anti-pollution devices, most notable is the catalytic converter, and has been given the nick name the "Environmental Metal". Native platinum is the primary ore of platinum, but deposits containing the rare platinum arsenide, sperrylite of the Pyrite Group, have made a huge contribution to the world's limited supply.

 Discovered by: Antonio de Ulloa

Discovered at: South America

Discovered when: 1735

Origin of name: From the Spanish word "platinum" meaning "silver"

 The metal was used by pre-Columbian Indians but platinum was "rediscovered" in South America by Ulloa in 1735 and by Wood in 1741. In 1822 plenty of platinum was discovered in the Ural Mountains in Russia.

The earliest known use of platinum as a decorative material is found on an Egyptian casket from the 7th century BC, now in the Louver, Paris. Ancient Egyptians mistook platinum for a corrupt silver. Platinum is the newest of the noble metals. It was not until 1557, following the Spanish conquest of South America, that the first references to it were published. During the Spanish conquest of South America, conquistadors threw platinum into the sea, in the hope that it would convert into silver, which they considered more valuable. Its name comes from 'platinum del Pinto', Spanish for 'little silver'. In 1751 a Swedish chemist named Schaffer recognized platinum as the

seventh element known to exist up until that time.

He was also the first to successfully melt platinum. Only aqua region, a combination of concentrated nitric and hydrochloric acids, can destroy platinum. "Royal water" was so named by the alchemists because of its ability to dissolve gold and other noble metals. On the introduction of the metric system in 1795, the standard meter and the standard kilogram were both measured in platinum.

The prototype international standard kilogram of mass was made from an alloy of 90 percent platinum and 10 percent iridium. Platinum has a liquid surface. When most metals, such as gold and silver, are polished or scratched, a small amount of material is lost. When platinum is scratched, however the metal has only moved aside so very little material is actually lost. Where platinum has been scratched, it will be harder and more resistant to being scratched again. The more platinum jeweler is worn, the harder and more durable it becomes. Platinum is so malleable that a single gram could be drawn into a fine wire stretching more than a mile long. Platinum, iridium and osmium are the densest known metals, platinum being 11 per cent denser than gold and about twice the weight of the same volume of silver or lead. Platinum is 60% heavier than gold.

Platinum has a very high melting point -- 1 769° C (3 216° F). This makes the manufacture of platinum jeweler much more demanding then gold or silver work. South Africa has more than 80 percent of the world's platinum, and controls more platinum reserves than all the Arab countries control oil reserves. Other major platinum producers are Colombia and Russia. Islamic religion forbids men to wear gold, but platinum is acceptable as its existence was unknown when Muhammad laid down the law.

In 1907 Louis Cartier made the first platinum watch. Pacemakers are made with platinum, and a platinum compound has been used for over twenty years to help arrest cancerous tumors. Until high-temperature jewelers' torches were developed early in the 20th century, industry and bullion coinage were major consumers of platinum. Platinum was first used for coins in Russia 1828. In 1865 some Spanish gold coins were counterfeited using gold plated platinum. The coronation crown of the British Queen Mother was made from platinum. One of platinum's essential uses is in vehicle catalytic converters, where it converts harmful emissions into carbon dioxide and water. Catalytic converters account for nearly one-third of newly mined platinum.

The first platinum investment coin, the one-ounce Noble from the Isle of Man, was introduced in November 1983. Other platinum coins are the Australian Koala, the Canadian Maple Leaf, the United States Platinum Eagle, the Russian Ballerina and the Chinese Panda - so beautiful that it is frequently incorporated into jewelers.

 Platinum-the preferred meta:  Platinum is the world's most precious metal, and one of its rarest. Prized for its pure white color, purity, and durability, it has many remarkable qualities and uses, from jeweler to pacemakers to the treatment of certain types of cancer. Elegant and subtle, platinum never competes with the color of a gem. Its deep white luster complements the stone's brilliance. It is the premium noble metal for our millennium, elegant and understated.                                        

          Although platinum was prominent in ancient Egyptian jewelers, and in early South American Aztec and Inca societies, it was mistaken for silver. Spaniards discovered it in Mexico in the 1500s, and although not pure, this was the first metal to be sourced from the 'New World'. It derives its name from the Spanish 'platinum', for silver of a lesser value. Early use of platinum was banned because it was used as a blank for coins which were subsequently gold coated. Platinum's classification as a metal in its own right -- in 1750 -- is comparatively recent.

The Platinum Age:  The Platinum Age began during the late 1700s, when a French goldsmith created platinum jeweler for King Louis XVI, who proclaimed it the only metal fit for royalty. One of the earliest decorative works of platinum, a glass-lined platinum sugar bowl dated 1786 and made by Marc Etienne Janet, a Parisian artist/metalworker, can be seen at the Metropolitan Museum of Art in New York City. In the late 1800s, modern jeweler icons Cartier, Faberge and Van Clef & Arpels used platinum in their legendary creations. Platinum readily adapted itself to the most daring designs, and no metal was as suited to complementing the exquisite gems found in the Kimberley diamond fields in the 1870s.Some of the most famous diamonds, such as the Hope and the Junker, are set in platinum. Today, however, platinum again charms and enchants a new generation of consumers who insist on one of earth's rarest gifts for their jeweler. Demy Moore, Whitney Houston, Marla Marples and Heather Locklear all chose platinum for their engagement or wedding rings.

 The ideal combination: South African platinum and diamonds are the ideal combination. Around 80 percent of the world's known platinum reserves are in South Africa's Northwest Province. Platinum is also ideal for setting softer precious stones, as it highly ductile.

Platinum is rare: only about 120 tons a year are produced, against more than 1 600 tons of gold. In fact, all the platinum ever found would make a cube just 5 metres long on each side, about the size of a two-car garage. It's rarity and value is expressed in the 'platinum' credit cards and awards. And the greatest commercial recognition a recording artist can receive is a 'platinum' disk denoting high sales. Platinum is difficult to mine and extract. Ten tons of ore must be mined to recover a single ounce, twice as much as gold. It takes about five months and over 150 elaborate steps to separate platinum from the ore and its 'sister' metals: iridium, osmium, palladium, rhodium and ruthenium. During World War II, platinum was declared an strategic metal, and its use in jeweler banned. White gold was used as a substitute until platinum became readily available again. Today, around 38 per cent of the world's platinum finds its way into jewelers.

 Pure and non-allergenic: In its pure form, platinum is soft and easy to work. However, it requires high temperatures and only melts at 1 769° C. It is usually alloyed with cobalt or other platinum group metals such as iridium or palladium to make is suitable for use in jeweler production. Platinum is easily corrupted by other metals, and has to be worked in the cleanest of environments by specialized jewelers.

Platinum is invariably extremely pure: jeweler stamped 'platinum 950' or '900' contains a minimum of 95 or 90 percent platinum. The remainder is usually another platinum group metal such as ruthenium or iridium. Jewelers stamped 'Triplet' indicates a particular combination: 90 percent platinum and 10 percent iridium. By comparison, 18 carat gold is 75 percent pure gold, and 14 carat gold is only 58 percent pure.One of the strongest and most enduring of metals, it is also one of the heaviest -- almost twice the weight of 18 carat gold. You can feel the difference. Platinum's purity makes it compatible with all skin types and it is hypoallergenic. If you have had a problem with gold in the past, consider this remarkable metal.

 Interesting facts:

• The coronation crown of the Queen Mother was made from platinum.
• The Kohinoor (Mountain of Light) diamond, part of the crown jewels is set in platinum.

• Around two tones of ore has to be mined to obtain enough platinum to make a ring.
• Platinum's melting point is almost double that of gold.
• Platinum is used in the hard discs of most PC's to improve capacity and durability.

• Platinum is resistant to attack from most chemicals.
• The only material suitable for the electrode in heart pacemakers is platinum.

• Platinum is used to make nitrogen fertilizers.
• 1 gram of platinum can be made into wire 2 kilometers long.
• Half of the platinum mined in the world in 2001 was made into jewelers.

• The Duke and Duchess of Windsor had platinum wedding rings made by Cartier.
• There is no platinum in a platinum record; it's only plastic dipped in silver.
• It takes 8 weeks to refine pure platinum from the ore extracted from the earth.

Mentor: Stojcevska Suzana

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