2. Mendelevium - how he started to creating periodic system 

In the middle of 19 century, Russia develop her hard and stain industry. Needs for metals were big. Parallel whit industry, develops science and technology .

Mendeleyev was born in Tobolsk, Siberia. In1850 he enrolled  in the Faculty of Physics and Mathematics of the Main Pedagogical Institute in Saint Petersburg, from which he graduated with a brilliant record in 1855. He taught  at the Odessa lyceum, where he continued work on the relationships between the crystal forms and the chemical composition of substances. In addition to his theoretical research, the application of science to industry and economics remained one of his primary concerns. He then worked  at the University of Heidelberg, where he first collaborated with Robert Bunsen and studied capillary phenomena and the deviations of gases and vapors from the ideal gas laws. In 1860, Mendeleyev discovered the concept of critical temperature and attended the first International Chemical Congress at Karlsruhe, where Stanislao Cannizzaro's views on atomic weights planted the seeds for the concept of the periodic table.

In 1864 Dimity Ivanovich Mendeleyev became a professor of on Technological institute. Four years later he was teaching technological chemistry on Petersburg’s university.  Like every teacher he had to decide how to prepare he's classes. But his mission was hard because of disorder between elements.  He need to gather all elements in some order. He had to  find the most clearing and the most logical exposure for 60, in that time, known elements. He collect a lot of chemistry books. Lavoisier and Berzelius was his guiders. Because he found no suitable text for his students, he wrote his own ''Principles of Chemistry'' (1868-71), which appeared in eight Russian, three English, and several French and German editions. His classes were so interest. Many students from the other groups visited them.

The systematization of ideas required for this book led Mendeleyev to formulate the periodic law in March 1869. The law organized the chemical elements known at the time according to their atomic weights and predicted the existence of more elements.

In subsequent years Mendeleyev refined and modified his law, which was received with considerable skepticism. In Russia in that time no one of Academics understands the greatness of his work.   His nomination for honored member of  Russian Academy of science was ignored , but public opinion was stoned of that. In one occasion he said : '' I am alone, so alone''.

After Paul Emile Lecoq de Boisbaudran, Lars Fredrik Nilsson, and Clemens Winkler discovered the elements gallium (1875), scandium (1879), and germanium (1886), respectively--whose existence was predicted by Mendeleyev in 1871--the periodic law was universally accepted.
 

  3. Davy 's rashness (anecdote)  

• Davy  was a big chemistry scientist who live at the end of XVIII century. He worked on alkali metals and he was the man who discover potassium end sodium. 

         He was completely dedicated on his work, but he won't pass any diner, party or bal at the town in which he was invited and sow his friends. He worked from early at the morning until evening when he recur that he must go at the party. 

        His friends spokes between themselves: - ''O, look at Mr. Davy, how quickly he became fat!!'' , but on next visit, whit surprise, they also says  - ''Do you notice how skinny he is now,?? How strange it is??''  

        But in all this is not secret. He worked hardly to announce his discovery. He hadn't time to wash himself and change dirty clouts, and then he dressed clean and white shirt above his dirty clouts. Sometimes he wear about dozen shirts, one under the other. When he finally finds free time, he unclothe all shirts and he was skinny again. Whit this he amazing his friends.

        Maybe this was only speculations, maybe not. Who knows?? 

5. Hydrogen    

      

	Hydrogen is known by the symbol H and has an electron configuration 1s1.It’s a colorless, odorless, tasteless gas. Hydrogen forms more compounds than any other element.

The great majority of these compounds are covalent, but the cation H⁺ is also very important chemically because of its role in acid-base reactions. Hydrogen is also a powerful reducing agent.

Hydrogen is the most abundant element in the universe. There is very little free hydrogen in the earth’s atmosphere, but large quantities are found in the combined state as water and organic compounds. Most hydrogen is manufactured from natural gas, which is composed largely of methane.

Hydrogen is a diatomic gas, which has the lowest density of all gases at room temperature and pressure. It is flammable. The splint test is used in the laboratory as a quick test for hydrogen, as this gas gives a mild explosive reaction in the presence of air. There are three isotopes of hydrogen:

- Protium - mass number 1

- Deuterium - mass number 2

- Tritium - mass number 3

Here are some chemical properties for the Hydrogen:

It’s covalently bonded in almost all its compounds. This is mainly because its ionization energy is very high, so the formation of H⁺ is not favoured. Also, H⁺ is a proton and so is extremely small, and this small size gives it exceptionally strong polarizing power. Important compounds containing hydrogen are discussed under the other element(s) concerned.

The cation H⁺ acts as an extremely strong Lewis acid in water and attaches strongly to a water molecule forming H₃O⁺. This ion plays a central role in the mechanism of acidbase reactions.

The most common oxidation number of hydrogen in its compounds is +1, eg: HCl, H₂O, but in compounds containing the hydride ion H^- it has an oxidation number of –1. In the industry the controlled explosive reaction between hydrogen and oxygen is used to power space vehicles.

Hydrogen is also used to reduce nitrogen gas to ammonia in the Haber-Bosch synthesis (see Group V). This is the principal method by which atmospheric nitrogen is brought into the food chain.

Ionisation Energy/kJ mol^-1 1312  ; Radius of H⁺ ion/m 10^-15 

6.  How big is Avogadro’s constant

         Avogadro’s constant is very famous and very big number. 

One university professor want to demonstrate to he’s student how big is Avogadro’s constant. In that purpose he want to transport one mol sand in university backyard. He takes agreement from university administration, but after that he confront whit one big problem.

Lets see what was that big problem.

-         In one mol there are 6,022 × 10²³ particles or around 10²⁴ particles.

-         In one cube meter sand, if the corns are cubes whit side 0,1 mm, there are (10⁴) ³ or 10¹² corns of sand.

-         10²⁴ particles sand, which contents in one mol, have volume:

10²⁴ corns / 10¹² corns in one cube meter sand = 10¹² m³

-         If the sand transport whit lorries and each of them can carry 10 m³, for 10¹² m³ sand needs:

10¹² m³ sand / 10 m³ for one lorry^-1 = 10¹¹ lorries whit sand

        The professor knows how much sand shoed be transport in the backyard. Only left how long the transporters can transport the sand. If every 10 minutes arrived one lorry, in 24 hours, how long time shod is need.

In one day will came 6 lorries * 24 hours = 144 lorries

144 lorries * 365,25 days / year = 52596 lorries in one year

-         At the last

10¹¹ lorries / 52596 lorries for one year  = 1901285,27 years or 19013 centuries 

Now it’s clear why the experiment can’t be presentation. The professor, exactly haven’t time to present the experiment.

SELF-TAUGHT SWEDISH chemist Karl Wilhelm Scheele was an apothecary assistant and experimented with chemicals in his spare time. Despite his unsystematic approach to research, he made many important discoveries. He was the first to identify and prepare oxygen, and also discovered chlorine, isolated phosphorus, and manganese and described the effect of light on certain silver salts – a process exploited 50 years later with the invention of photography. Much of Scheele’s work anticipated that of more famous chemists working in France and England, but because he did not have an academic position and delayed in publishing his work, he did not receive the recognition he deserved.

           Self-taught, Carl Wilhelm Scheele was born December of 9, 1742. He began his study of chemistry while apprenticed (1757-1765) to an apothecary in Goteborg on 14 years age. From 1765 to 1774 he worked as a pharmacist in Malmo, Stockholm, and Uppsala. In 1775 he moved to Koping as proprietor of a pharmacy.

He wasn’t educated, he haven’t assistant, and he learned alone and made his primitive apparaturs from thinks around him, but he was born chemist. He wants to know, from what everything is made.

 At the beginning he research whit many acids and alkalis. Once he succeeds made a gas whit aroma on bitter almond. He smelled and tested the gas to research the aroma. It’s not aloud to repeat that to nobody, because that gas was HCN – hydrogen cyanide, a very poison gas. Although the gas was strong poison, he was very happy, because he was the first man who says this substance. In one occasion he say: Researcher is happy when he find what he look for. He’s heart is fulfilled. He remained there the rest of his life, declining an offer from Frederick the Great of a chair in chemistry at Berlin and an offer of a similar position in England.

Scheele was a prolific and careful experimentalist. He was the first to identify calcium phosphate as a component of bone and to show that lactic acid was the cause of milk's turning sour. In working with minerals, Scheele obtained chlorine, manganese, and hydrofluoric acid and silicon fluoride from fluorspar. He also prepared molybdic acid, tungstic acid, arsenic acid, arsine, and copper arsenite (Scheele's green). From plant and animal sources Scheele obtained and purified a number of organic acids as well as glycerol, acetaldehyde, and a number of esters. He prepared and investigated hydrogen sulfide.

Nineteen years after he began his carrier he was elected by Swedish academy for honor member, but he was still one simple laboratories.  

          His early death resulted from complications following several disorders, including rheumatism and gout. He dies May of 21, 1786 

  8.  Table of detection

  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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