Palladium (46)

Palladium is a steel-white metal, does not tarnish in air, and is the least dense and lowest melting of the platinum group metals. When annealed, it is soft and ductile. Cold working increases its strength and hardness. It is used in some watch springs.

Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM).

At room temperatures the metal has the unusual property of absorbing up to 900 times its own volume of hydrogen. Hydrogen readily diffuses through heated palladium and this provides a means of purifying the gas.

•Name: Palladium
•Symbol: Pd
•Atomic number: 46
•Atomic weight: 106.42
•Standard state: solid at 298 K

•CAS Registry ID: 7440-05-3
•Group in periodic table: 10
•Group name: Precious metal or Platinum group metal
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery white metallic
•Classification: Metallic

Historical information

Palladium was discovered by William Hyde Wollaston at 1803 in England. Origin of name is from after the asteroid "Pallas" which was discovered at about the same time, and from the Greek name "Pallas", goddess of wisdom. William Hyde Wollaston discovered palladium in 1803-1804 in crude platinum ore from South America. He dissolved the ore in aqua regia (a mixture of hydrochloric [HCl] and nitric [HNO3] acids), neutralized the acid with sodium hydroxide (NaOH), and precipitated the platinum by treatment with ammonium chloride [NH4Cl] as ammonium chloroplatinate. Palladium was then removed as palladium cyanide by treatment with mercuric cyanide. The metal was produced from this cyanide by heating.

Physical properties

•Melting point: 1828.05 [or 1554.9 °C (2830.82 °F)] K
•Boiling point: 3236 [or 2963 °C (5365 °F)] K
•Density of solid: 12023 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d10
•Shell structure: 2.8.18.18.0
•Term symbol: 1S0

Isolation

It would not normally be necessary to make a sample of palladium in the laboratory as the metal is available commercially. The industrial extraction of palladium is complex as the metal occurs in ores mixed with other metals such as platinum. 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 palladium is the basis of important catalysts in industry.

Preliminary treatment of the ore or base metal byproduct with aqua regia gives a solution containing complexes of gold and platinum as well as H2PdCl4. The gold is removed from this solution as a precipitate by treatment with iron (II) chloride (FeCl2). The platinum is precipitated out as platinum ammonium chloride [(NH4)2PtCl6] on treatment with NH4Cl, leaving H2PdCl4 in solution. The palladium is precipitated out by treatment with ammonium hydroxide, NH4OH, and HCl as the complex PdCl2(NH3)2. This yields palladium metal by burning.

Rhodium (45)

Rhodium metal is silvery white. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. Upon heating it turns to the oxide when red and at higher temperatures turns back to the element. It is a major component of industrial catalytic systems such as the BP-Monsanto process.

Ruthenium, rhodium, palladium, osmium, iridium, and platinum ...together make up a group of elements referred to as the platinum group metals (PGM).

•Name: Rhodium
•Symbol: Rh
•Atomic number: 45
•Atomic weight: 102.90550 (2)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-16-6
•Group in periodic table: 9
•Group name: Precious metal or Platinum group metal
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery white metallic
•Classification: Metallic

Historical information

Rhodium was discovered by William Hyde Wollaston at 1803 in England. Origin of name: from the Greek word "rhodon" meaning "rose". William Hyde Wollaston discovered rhodium in 1803-4 in crude platinum ore from South America rather soon after his discovery of another element, palladium. He dissolved the ore in aqua regia (a mixture of hydrochloric and nitric acids), neutralised the acid with sodium hydroxide (NaOH), and precipitated the platinum by treatment with ammonium chloride, NH4Cl, as ammonium chloroplatinate. Palladium was then removed as palladium cyanide by treatment with mercuric cyanide. The remaining material was a red material containing rhodium chloride salts from which rhodium metal was obtained by reduction with hydrogen gas.

 

Physical properties

•Melting point: 2237 [or 1964 °C (3567 °F)] K

•Boiling point: 3968 [or 3695 °C (6683 °F)] K

•Density of solid: 12450 kg m-3

 

Orbital properties

•Ground state electron configuration: [Kr].4d85s1

•Shell structure: 2.8.18.16.1

•Term symbol: 4F9/2

 

Isolation

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

 

Preliminary treatment of the ore or base metal byproduct is required to remove silver, gold, palladium, and platinum. The resulting residue is melted with sodium bisulphate (NaHSO4) and the resulting mixture extracted water to give a solution containing rhodium sulphate, Rh2(SO4)3. The rhodium is precipitated out as the hydroxide by addition of sodium hydroxide, NaOH, and redissolved in hydrochloric acid, HCl, to give H3RhCl6. This is treated with NaNO2 and NH4Cl to form a precipitate of the rhodium complex (NH4)3[Rh(NO2)6]. Dissolution of the precipitate in HCl gives a solution of pure (NH4)3RhCl6. Evaporation to dryness and burning under hydrogen gas gives pure rhodium.

Ruthenium (44)

Ruthenium is a hard, white metal. It does not tarnish at room temperatures, but oxidizes in air at about 800°C. The metal is not attacked by hot or cold acids or aqua regia, but when potassium chlorate is added to the solution, it oxidizes explosively.

Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM).

•Name: Ruthenium
•Symbol: Ru
•Atomic number: 44
•Atomic weight: 101.07
•Standard state: solid at 298 K
•CAS Registry ID: 7440-18-8
•Group in periodic table: 8
•Group name: Precious metal or Platinum group metal
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery white metallic
•Classification: Metallic

Historical information

Ruthenium was discovered by Karl Karlovich Klaus at 1844 in Russia. Origin of name is from the Latin word "Ruthenia" meaning "Russia". Ruthenium was isolated in 1844 by Karl Karlovich Klaus, who obtained ruthenium from the part of crude platinum that is insoluble in aqua regia (very cool cleaning solution made up of two acids - nitric and hydrochloric). It is possible that a Polish chemist Jedrzej Sniadecki had in fact isolated ruthenium from some platinum ores rather earlier than this in 1807 but his work was not ratified, apparently as he withdrew his claims. He called it vestium.

Physical properties

•Melting point: 2607 [or 2334 °C (4233 °F)] K
•Boiling point: 4423 [or 4150 °C (7502 °F)] K
•Density of solid: 12370 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d75s1
•Shell structure: 2.8.18.15.1
•Term symbol: 5F5

Isolation

It would not normally be necessary to make a sample of ruthenium in the laboratory as the metal is available, at a price, commercially. The industrial extraction of ruthenium is complex as the metal occurs in ores mixed with other metals such as rhodium, palladium, silver, platinum, and gold. Sometimes extraction of the precious metals such as iridium, rhodium, platinum and palladium is the main focus of a particular industrial operation while in other cases it is a byproduct. The extraction is complex because of the other metals present and only worthwhile since ruthenium is useful as a specialist metal and is the basis of some catalysts in industry.

Preliminary treatment of the ore or base metal byproduct is required to remove silver, gold, palladium, and platinum. The residue is melted with sodium bisulfate (NaHSO4) and the resulting mixture extracted with water to give a solution containing rhodium sulphate, Rh2(SO4)3. The insoluble residue contains the ruthenium. The residue is melted with Na2O2 and extracted into water to extract the ruthenium and osmium salts (including [RuO4]2- and [OsO4(OH)2]2-). The residue contains iridium oxide, IrO2. Reaction of the salt with chlorine gas gives the volatile oxides RuO4 and OsO4. The ruthenium oxide is dissolved by treatment with hydrochloric acid to form H3RuCl6, and the ruthenium precipitated out as pure (NH4)3RuCl6 by treatment with NH4Cl. Evaporation to dryness and burning under hydrogen gas gives pure ruthenium.

Technetium (43)

Since its discovery, searches for the element technetium [TEK-NET-EE-UM] in terrestrial materials have been made without success. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars.

Technetium is a silvery-grey metal that tarnishes slowly in moist air. Until 1960, technetium was available only in small amounts. The chemistry of technetium is related to that of rhenium.

•Name: Technetium
•Symbol: Tc
•Atomic number: 43
•Atomic weight: [ 98 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-26-8
•Group in periodic table: 7
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery grey metallic
•Classification: Metallic

Historical information

Technetium was discovered by Carlo Perrier, Emilio Segre at 1937 in Italy. Origin of name is from the Greek word "technikos" meaning "artificial". Element 43 (technetium) was predicted on the basis of the periodic table by Mendeleev. He suggested that it should be very similar to manganese and gave it the name ekamanganese. Technetium was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by C. Perrier and Emilio Gino Segre in Italy in 1937. It was found in a sample of molybdenum bombarded by deuterons. Technetium was the first element to be produced artificially and all its isotopes are radioactive. It is named after the Greek technetos, artificial.

Physical properties

•Melting point: 2430 [or 2157 °C (3915 °F)] K
•Boiling point: 4538 [or 4265 °C (7709 °F)] K
•Density of solid: 11500 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d6.5s1
•Shell structure: 2.8.18.14.1
•Term symbol: 6S5/2

Isolation

It is never necessary to make a sample of technetium anywhere other than specialist laboratories. This is because technetium is radioactive. Technetium is a byproduct of the nuclear industry and is a product of uranium decay. Alternatively it can be made by the bombardment of molydenum targets with deuterium nuclei.

Because of the scale of the nuclear industry it is possible to make quite large quantities of technetium (kilograms). The metal itself may be made by the reaction of the sulfide Tc2S7 with hydrogen at 1100°C or of the pertechnate NH4TcO4 with hydrogen.

Molybdenum (42)

Molybdenum (MO-LIB-DEN-UM) is a silvery-white, hard, transition metal. Scheele discovered it in 1778. It was often confused with graphite and lead ore. Molybdenum is used in alloys, electrodes and catalysts. The World War 2 German artillery piece called "Big Bertha" contains molybdenum as an essential component of its steel.

•Name: Molybdenum
•Symbol: Mo
•Atomic number: 42
•Atomic weight: 95.96
•Standard state: solid at 298 K
•CAS Registry ID: 7439-98-7
•Group in periodic table: 6
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: grey metallic
•Classification: Metallic

Historical information

Molybdenum was discovered by Carl William Scheele at 1781 in Sweden. Origin of name is from the Greek word "molybdos" meaning "lead". In 1778 Carl Welhelm Scheele conducted research on an ore now known as molybdenite. He concluded that it did not contain lead as was suspected at the time and reported that the mineral contained a new element that he called molybdenum after the mineral. Molybdenum metal was prepared in an impure form in 1782 by Peter Jacob Hjelm.

Physical properties

•Melting point: 2896 [or 2623 °C (4753 °F)] K
•Boiling point: 4912 [or 4639 °C (8382 °F)] K
•Density of solid: 10280 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d5.5s1
•Shell structure: 2.8.18.13.1
•Term symbol: 7S3

Isolation

It is not normally necessary to make samples of molybdenum metal in the laboratory since it is readily available commercially. Industrially, its extraction is sometimes linked to copper production. The normal process is for the sulfide MoS2 to be "roasted" to form the oxide MoO3. This is often used directly in the steel industry.

Pure samples of the metal are available by first dissolving the oxide in ammonium hydroxide to make ammonium molybdate, (NH4)2[MO4], and then reduction of the molybdate with hydrogen gas to form the metal.

Niobium (41)

The name niobium was adopted officially by IUPAC in 1950, but a few commercial producers still like to refer to it as columbium. Niobium is a shiny, white, soft, and ductile metal, and takes on a bluish tinge when exposed to air at room temperatures for a long time. The metal starts to oxidize in air at high temperatures, and when handled hot must be done so under a protective atmosphere so as to minimize oxide production.

•Name: Niobium
•Symbol: Nb
•Atomic number: 41
•Atomic weight: 92.90638 (2)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-03-1
•Group in periodic table: 5
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: grey metallic
•Classification: Metallic

Historical information

Niobium was discovered by Charles Hatchett at 1801 in England. Origin of name: from the Greek word "Niobe" meaning "daughter of Tantalus" (tantalum is closely related to niobium in the periodic table). Niobium was discovered in 1801 by Charles Hatchett in an ore called columbite sent to England in the 1750s by John Winthrop the Younger, the first governor of Connecticut, USA. Hatchett called the new element columbium. He was not able to isolate the free element. There was then considerable confusion concerning the distinction between niobium and tantalum as they are so closely related. This confusion was resolved by Heinrich Rose, who named niobium, and Marignac in 1846. The name niobium is now used in place of the original name "columbium".

The metal niobium was first prepared in 1864 by Blomstrand, who reduced the chloride by heating it in a hydrogen atmosphere.

Physical properties

•Melting point: 2750 [or 2477 °C (4491 °F)] K
•Boiling point: 5017 [or 4744 °C (8571 °F)] K
•Density of solid: 8570 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d4.5s1
•Shell structure: 2.8.18.12.1
•Term symbol: 6D1/2

 

Isolation

Isolation of niobium appears to be complicated. Niobium minerals usually contain both niobium and tantalum. Since they are so similar chemically, it is difficult to separate them. Niobium can be extracted from the ores by first fusing the ore with alkali, and then extracting the resultant mixture into hydrofluoric acid, HF. Current methodology involves the separation of tantalum from these acid solutions using a liquid-liquid extraction technique. In this process tantalum salts are extracted into the ketone MIBK (methyl isobutyl ketone, 4-methyl pentan-2-one). The niobium remains in the HF solution. Acidification of the HF solution followed by further extraction in MIBK gives an organic solution containing niobium.

Zirconium (40)

Zirconium is a greyish-white lustrous metal. The finely divided metal can ignite spontaneously in air, especially at elevated temperatures. The solid metal is much more difficult to ignite. The inherent toxicity of zirconium compounds is low. Hafnium is invariably found in zirconium ores, and the separation is difficult. Commercial grade zirconium contains from 1 to 3% hafnium. The hafnium is removed from the zirconium used in the nuclear power industry.

Zirconium is found in S-type stars, and has been identified in the sun and meteorites. Analyses of lunar rock samples show a surprisingly high zirconium oxide content as compared with terrestrial rocks. Some forms of zircon (ZrSiO4) have excellent gemstone qualities.

•Name: Zirconium
•Symbol: Zr
•Atomic number: 40
•Atomic weight: 91.224 (2)
•Standard state: solid at 298 K
•CAS Registry ID: 7440-67-7
•Group in periodic table: 4
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery white
•Classification: Metallic

Historical information
Zirconium was discovered, in its impure form, by Martin Heinrich Klaproth at 1789 in Berlin, Germany. Origin of name is from the Arabic word "zargun" meaning "gold color," which describes the color of the gemstone now known as zircon (ZrSiO4). The minerals jargon, hyacinth, and jacinth also contain zircon and these have been known since biblical times and are mentioned in the bible in several places. The existence of a new element within these minerals was not suspected until studies by Martin Heinrich Klaproth in the late 18th century.

The impure metal was first isolated by Jöns Jacob Berzelius in 1824 who heated a mixture of potassium and potassium zirconium fluoride together in an iron tube. Pure zirconium was first prepared in 1914.

Physical properties
•Melting point: 2128 [or 1855 °C (3371 °F)] K
•Boiling point: 4682 [or 4409 °C (7968 °F)] K
•Density of solid: 6511 kg m-3

Orbital properties
•Ground state electron configuration: [Kr].4d2.5s2
•Shell structure: 2.8.18.10.2
•Term symbol: 3F2

Isolation
Zirconium is available from commercial sources so preparation in the laboratory is not normally required. In industry, reduction of ores with carbon is not a useful option as intractable carbides are produced. As for titanium, the Kroll method is used for zirconium and involves the action of chlorine and carbon upon baddeleyite (ZrO2). The resultant zirconium tetrachloride, ZrCl4, is separated from the iron trichloride, FeCl3, by fractional distillation. Finally ZrCl4 is reduced to metallic zirconium by reduction with magnesium (Mg). Air is excluded so as to prevent contamination of the product with oxygen or nitrogen.

ZrO2 + 2Cl2 + 2C (900°C) → ZrCl4 + 2CO

ZrCl4 + 2Mg (1100°C) → 2MgCl2 + Zr

Excess magnesium and magnesium dichloride is removed from the product by treatment with water and hydrochloric acid to leave a zirconium "sponge". This can be melted under helium by electrical heating.

FUN FACTS!
•Australia, Brazil, India, Russia and the USA are the major locations where zirconium deposits are found.
•It is abundant in S-type stars and its existence has also been detected in the Sun and the meteorites.
•The abundance of this metal in lunar rock samples has been found to be higher than what is found in terrestrial rocks.
•As a transition metal, zirconium is a good conductor of heat and fire. It also scores well on malleability and ductility.
•The metal has an atomic radius (pm) of 160 and Ionic radius of 790(+4e).
•Its lattice structure is hexagonal, and it has a lattice constant of 3.230.
•Specific heat is 0.281 @20°C J/g mol, and fusion heat is 19.2 (kJ/mol).
•Zirconium in powder form is highly susceptible to combustion, however, far less when in solid form.
•Alkalis, acids, salt water and many other agents have no corrosive effects on zirconium. However, if combined with hydrochloric and sulfuric acid, it will dissolve. This reaction becomes faster in the presence of fluorine.
•Inhalation of the compounds of this metal may cause skin and lung granulomas (a tumor composed of granulation tissue resulting from injury or inflammation or infection). Minor skin irritation has also been reported due to contact with zirconium powder. If it comes in contact with eyes, then it may warrant medical attention.
•The metal attains the property of a superconductor (a conductor that offers zero resistance to current; for this it must attain a certain temperature called the "critical temperature") when alloyed with niobium (soft, gray, ductile transition metal - more to come soon).
•The metal shares similar properties with titanium. However, the former has higher density and melting temperature than that of the latter.

Uses for Zirconium

# Zirconium is the source of the closest mimic of diamond - Cubic Zirconia (CZ). It is popularly fashioned as a diamond simulant (non-diamond material).

# Given the metal's low absorption of neutrons, and significant resistant towards heat and chemical corrosion, it is widely used in the working of nuclear reactors. Here the metal is used to provide an outer covering to components such as the fuel rods that run the reactor. As a matter of fact the nuclear power industry exploits 90% of the metal produced each year.

# As the metal is extremely high on the corrosion-resistance factor, it finds its applications in many industries which make use of corrosive agents such as in high-performance pumps, valves, etc.

# Zirconium oxide or zirconia, is mainly used in the manufacture of ceramic materials. It is an inorganic metal oxide, and a compound of zirconium. It is also used as a gemstone as it has a high refractive index.

# The main sources of zirconium are the minerals called zircon (ZrSiO4) and baddeleyite (ZrO2). A process known as the Kroll process is applied to obtain the metal from these minerals.

# Another use of zirconium is evident by black zirconium rings. These rings are available in elegant and luxurious designs for fashion-conscious people. These rings are scratch-resistant and do not sustain the wear and tear unlike other common metals.

# A common ingredient in antiperspirant is aluminum zirconium. It is, however, related to the development of breast cancer and Alzheimer's Disease. But there is no solid evidence to back this fact, and there are many controversies regarding the ill effects of the same.

# Zirconium also finds its application in steel as an alloying agent. Vacuum tubes, different surgical appliances, lamp filaments, piping, artificial joints and limbs require this metal. Apart from these, the metal is employed in photoflash bulbs, explosive primers, rayon spinnerets, etc.

Yttrium (39)

Yttrium (IT-REE-UM) has a silvery-metallic luster. Yttrium turnings ignite in air. Yttrium is found in most rare-earth minerals. Moon rocks contain yttrium and yttrium is used as a "phosphor" to produce the red color in television screens.

•Name: Yttrium
•Symbol: Y
•Atomic number: 39
•Atomic weight: ...88.90585
•Standard state: solid at 298 K
•CAS Registry ID: 7440-65-5
•Group in periodic table: 3
•Period in periodic table: 5
•Block in periodic table: d-block
•Color: silvery white
•Classification: Metallic

Historical information

Yttrium was discovered by Johann Gadolin at 1794 in Finland. Origin of name is the village of "Ytterby" near Vaxholm in Sweden. Yttria (yttrium oxide, Y2O3), was discovered by Johann Gadolin in 1794 in a mineral called gadolinite from Ytterby. Ytterby is the site of a quarry in Sweden which contains many unusual minerals containing erbium, terbium, and ytterbium as well as yttrium. Friedrich Wohler obtained the impure element in 1828 by reduction of the anhydrous chloride (YCl3) with potassium.

Physical properties

•Melting point: 1799 [or 1526 °C (2779 °F)] K
•Boiling point: 3609 [or 3336 °C (6037 °F)] K
•Density of solid: 4472 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].4d1.5s2
•Shell structure: 2.8.18.9.2
•Term symbol: 2D3/2

Isolation

Yttrium metal is available commercially so it is not normally necessary to make it in the laboratory. Yttrium is found in lathanoid minerals and the extraction of the yttrium and the lanthanoid metals from the ores is highly complex. Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures involve selective complexation techniques, solvent extractions, and ion exchange chromatography.

Pure yttrium is available through the reduction of YF3 with calcium metal.

2YF3 + 3Ca → 2Y + 3CaF2

Interesting Facts...

Yttrium (English/French/German/Swedish) Ittrio (Italian) Ytrio (Spanish)

Yttrium is often used to make alloys with other metals. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. Two of yttrium's most interesting applications are in lasers and superconducting materials.

A laser is a device for producing very bright light of a single color. One of the most popular lasers is made of yttrium, aluminum, and garnet. One of the most widely used lasers today is the yttrium-aluminum-garnet (YAG) Laser. YAG Lasers often contain other elements. These elements change the kind of light produced by the laser in one way or another. The Laser is said to be doped with another element if it contains a small amount of that element. An example of this kind of laser is one doped with neodymium. The neodymium-doped YAG (Nd:YAG) laser has been used to make Long distance measurements (for my 2171 friends - think of the MULE and the range finders).

Garnet is a gem-like material with a sand-like composition. Superconducting materials are substances with no resistance to the flow of an electric current. An electric current that begins to flow through them never stops. Superconducting materials may have many very important applications in the future.

Yttrium phosphors have long been used in color television sets and in computer monitors.

None of the radioactive isotopes of yttrium has any important commercial use. However, yttrium-90 is now being tested as a treatment for cancer. Radiation given off by the isotope kills cancer cells. Researchers believe that yttrium-90 may find wider use in the future for treating cancer. One advantage of using this isotope is that is easy to obtain. It is produced when another radioactive isotope (strontium-90) breaks down. Strontium-90 is a by-product formed in nuclear power plants.

Strontium (38)

Strontium does not occur as the free element. Strontium is softer than calcium and decomposes water more vigorously. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish color with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart an excellent crimson color to flames, and these salts are used in pyrotechnic...s (fireworks, for example).

The different colors are a result of adding different metal salts to a burning reaction mixture of potassium chlorate and sucrose. The red color originates from strontium sulphate. The orange/yellow color originates from sodium chloride. The green color originates from barium chlorate and the blue color originates from copper (I) chloride. The lilac color that should be evident from the potassium chlorate is washed out by the other colors, all of which are more intense (only to be demonstrated by a professionally qualified chemist following a legally satisfactory hazard assessment). Improperly done, this reaction is dangerous!

The picture above shows the color arising from adding strontium sulphate salt (SrSO4) to a burning mixture of potassium chlorate and sucrose. Do not attempt this reaction unless are a professionally qualified chemist and you have carried out a legally satisfactory hazard assessment (leave it to the professionals!).

Strontium-90 (90Sr) has a half-life of 28 years. It is a product of nuclear fallout and presents a major health problem. Strontium titanate is an interesting optical material as it has an extremely high refractive index and an optical dispersion greater than that of diamond. It has been used as a gemstone, but it is very soft.

•Name: Strontium
•Symbol: Sr
•Atomic number: 38
•Atomic weight: 87.62
•Standard state: solid at 298 K
•CAS Registry ID: 7440-24-6
•Group in periodic table: 2
•Group name: Alkaline earth metal
•Period in periodic table: 5
•Block in periodic table: s-block
•Color: silvery white
•Classification: Metallic

Historical information

Strontium was discovered by Adair Crawford at 1790 in Scotland. Origin of name is after the village of "Strontian" in Scotland. Adair Crawford in 1790 recognized a new mineral (strontianite) in samples of witherite (a mineral consisting of barium carbonate, BaCO3) from Scotland. It was some time before it was recognized that strontianite contained a new element. Strontianite is now known to consist of strontium carbonate, SrCO3. The element itself was not isolated for a number of years after this when strontium metal was isolated by Davy by electrolysis of a mixture containing strontium chloride and mercuric oxide in 1808.

Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for strontium is a circle with dashes at the N, E, S, W quarters (kind of like a sighting reticle on guns/rifles)

Physical properties

•Melting point: 1050 [or 777 °C (1431 °F)] K
•Boiling point: 1655 [or 1382 °C (2520 °F)] K
•Density of solid: 2630 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].5s2
•Shell structure: 2.8.18.8.2
•Term symbol: 1S0

Isolation

Strontium metal is available commercially and there is no need to make it in the laboratory. Commercially it is made on small scale by the electrolysis of molten strontium chloride, SrCl2.

Cathode: Sr2+(l) + 2e- → Sr                                         Anode: Cl-(l) → 1/2Cl2 (g) + e-

Strontium metal can also be isolated from the reduction of strontium oxide, SrO, with aluminum.

6SrO + 2Al → 3Sr + Sr3Al2O6

Rubidium (37)

Rubidium can be liquid at ambient temperature, but only on a hot day given that its melting point is about 40°C. It is a soft, silvery-white metallic element of the alkali metals group (Group 1). It is one of the most electropositive and alkaline elements. It ignites spontaneously in air and reacts violently with water, setting fire to the liberated hydrogen. As so with all the other alkali metals, it forms amalgams with mercury. It alloys with gold, cesium, sodium, and potassium. It colors a flame yellowish-violet.

•Name: Rubidium
•Symbol: Rb
•Atomic number: 37
•Atomic weight: 85.4678
•Standard state: solid at 298 K
•CAS Registry ID: 7440-17-7
•Group in periodic table: 1
•Group name: Alkali metal
•Period in periodic table: 5
•Block in periodic table: s-block
•Color: silvery white
•Classification: Metallic

Historical information

Rubidium was discovered by Robert Bunsen, Gustav Kirchhoff at 1861 in Germany. Origin of name is from the Latin word "rubidius" meaning "dark red" or "deepest red". Rubidium was discovered in 1861 spectroscopically by Robert Bunsen and Gustav Kirchoff as an impurity associated with samples of the mineral lepidolite (a form of mica). The name rubidium (from the Latin "rubidus" - dark red) was coined for its bright red spectroscopic lines (pretty!).

Rubidium salts were isolated by Bunsen by precipitation from spring waters - along with salts of other Group 1 elements. He was able to separate them and isolated the chloride and the carbonate. He isolated rubidium metal by reducing rubidium hydrogen tartrate with carbon.

Physical properties

•Melting point: 312.46 [or 39.31 °C (102.76 °F)] K
•Boiling point: 961 [or 688 °C (1270 °F)] K
•Density of solid: 1532 kg m-3

Orbital properties

•Ground state electron configuration: [Kr].5s1
•Shell structure: 2.8.18.8.1
•Term symbol: 2S1/2

Isolation

Rubidium would not normally be made in the laboratory as it is available commercially. All syntheses require an electrolytic step as it is so difficult to add an electron to the poorly electronegative rubidium ion Rb+.

Rubidium is not made by the same method as sodium as might have been expected. This is because the rubidium metal, once formed by electrolysis of liquid rubidium chloride (RbCl), is too soluble in the molten salt.

Cathode: Rb+(l) + e- → Rb (l)                                                                      Anode: Cl-(l) → 1/2Cl2 (g) + e-

Instead, it is made by the reaction of metallic sodium with hot molten rubidium chloride.

Na + RbCl ⇌ Rb + NaCl

This is an equilibrium reaction and under these conditions the rubidium is highly volatile and removed from the system in a form relatively free from sodium impurities, allowing the reaction to proceed.

Krypton (36)

No - it's not about Superman at all...

Krypton is present in the air at about 1 ppm. The atmosphere of Mars contains a little (about 0.3 ppm) of krypton. It is characterized by its brilliant green and orange spectral lines. The spectral lines of krypton are easily produced and some are very sharp. In 1960 it was internationally agreed that the fundamental unit of length, the meter, should be defined as 1 m = 1,650,763.73 wavelengths (in vacuo) of the orange-red line of Kr-33.

Under normal conditions krypton is colorless, odorless, fairly expensive gas. Solid krypton is a white crystalline substance with a face-centered cubic structure which is common to all the "rare gases". Krypton difluoride, KrF2, has been prepared in gram quantities and can be made by several methods.

•Name: Krypton
•Symbol: Kr
•Atomic number: 36
•Atomic weight: 83.798
•Standard state: gas at 298 K
•CAS Registry ID: 7439-90-9
•Group in periodic table: 18
•Group name: Noble gas
•Period in periodic table: 4
•Block in periodic table: p-block
•Color: colorless
•Classification: Non-metallic

Historical information

Krypton was discovered by Sir William Ramsay, Morris W. Travers at 1898 in Great Britain. Origin of name is from the Greek word "kryptos" meaning "hidden." Krypton was discovered in 1898 by Sir William Ramsay and his student Morris Travers in the residue left after liquid air had nearly boiled away. Krypton was left in the residue after boiling away water, oxygen, nitrogen, helium, and argon from the sample of air. Krypton is present in the air at about 1 ppm. Neon was discovered by a similar procedure by the same workers just a few weeks later.

Physical properties

•Melting point: 115.79 [or -157.36 °C (-251.25 °F)] K
•Boiling point: 119.93 [or -153.22 °C (-243.8 °F)] K
•Density of solid: 2155 kg m-3

Orbital properties

•Ground state electron configuration: [Ar].3d10.4s2.4p6
•Shell structure: 2.8.18.8
•Term symbol: 1S0

Isolation

Krypton is present to a small extent (about 1 ppm by volume) in the atmosphere and is obtained as a byproduct from the liquefaction and separation of air. This would not normally be carried out in the laboratory and krypton is available commercially in cylinders at high pressure.

Interesting Facts:

Krypton (English, French, German, Swedish) Cripto (Italian) Kriptón (Spanish)

•Krypton has 31 isotopes in all, out of which 5 are stable and the rest are radioactive.

•The half-life of radioactive krypton, 81Kr is 250,000 years.

•Krypton is produced in the Earth's crust as a result of radioactive decay of thorium and uranium.

•As most of the nuclear reactors are located in the northern hemisphere, the concentration of krypton at the north pole is about 30% higher than that at the south pole.

•The element Krypton is characterized by emission of sharp spectral lines, out of which, the green and yellow lines are the strongest and most prominent.

•When ionized, krypton gas emits bright white light, and hence krypton based bulbs are widely used in high speed photography. It is also used in slide and movie projectors.

•Krypton, like other inert gases, is used in making luminous, fluorescent lights used in different kinds of lamps, incandescent light bulbs, advertising signs, etc.

•One of the radioactive isotopes of krypton, can be combined with phosphorus to produce materials that glow or shine in the dark.

•Krypton-85, is used to study the flow of blood in the human body. When the gas is inhaled, it is absorbed by the blood and travels through the bloodstream and the heart along with blood. The pathway can be determined by holding a detection device over the person’s body.

•Krypton is used in the manufacture of quasi-homogeneous electromagnetic calorimeters, which are used to measure the quantity of heat.

•An interesting application of krypton gas was in defining a meter. Krypton-86, on heating gives off a clear bright line, which is reddish yellow in color. Between the period of 1960 and 1980, scientists defined meter as 1,650,763.73 times the width of this line produced by krypton.

•Krypton is considered to be one of the inert gases, which means it is chemically inactive. However, compounds of krypton have been synthesized in the laboratory and these synthetic compounds of krypton are used for research purpose

Bromine (35)

Bromine is the only liquid nonmetallic element. It is a member of the halogen group. It is a heavy, volatile, mobile, dangerous reddish-brown liquid. The red vapor has a strong unpleasant odor and the vapor irritates the eyes and throat. It is a bleaching. When spilled on the skin it produces painful sores. It is a serious health hazard, and maximum safety precautions should be taken when handling it.

•Name: Bromine
•Symbol: Br
•Atomic number: 35
•Atomic weight: 79.904
•Standard state: liquid at 298 K
•CAS Registry ID: 7726-95-6
•Group in periodic table: 17
•Group name: Halogen
•Period in periodic table: 4
•Block in periodic table: p-block
•Color: red-brown, metallic luster when solid
•Classification: Non-metallic

Historical information

Bromine was discovered by Antoine-J. Balard in France, 1826. Origin of nameis from the Greek word "bromos" meaning "stench." Bromine was not prepared in quantity until 1860 but compounds of bromine were of some considerable importance well before it was recognized as an element. Long ago an excretion from a particular kind of mussel was used to make a purple dye called "Tyrian purple". It is now known that a key compound in this process is an organobromine compound.

It seems that an undergraduate chemist called Carl Löwig studying at Heidelberg presented one of his lecturers, Leopold Gmelin, with a sample of bromine that he had made over the summer holidays. Löwig's exams interrupted his studies long enough to allow a report from Antoine-Jérôme Balard to take precedence in 1826.

Physical properties

•Melting point: 265.8 [or -7.3 °C (19 °F)] K
•Boiling point: 332 [or 59 °C (138 °F)] K
•Density of solid: 4050 kg m-3

Orbital properties

•Ground state electron configuration: [Ar].3d10.4s2.4p5
•Shell structure: 2.8.18.7
•Term symbol: 2P3/2

Isolation

Bromine is available commercially so it is not normally necessary to make it in the laboratory. Bromine also occurs in seawater as the sodium salt but in much smaller quantities than chloride. It is recovered commercially through the treatment of seawater with chlorine gas and flushing through with air. In this treatment, bromide is oxidized to bromine by the chlorine gas. The principle of oxidation of bromide to bromine is shown by the addition of a little chlorine water to aqueous solutions of bromide. These become brown as elemental bromine forms.

2Br- + Cl2 → 2Cl- + Br2

Small amounts of bromine can also be made through the reaction of solid sodium bromide, NaBr, with concentrated sulphuric acid, H2SO4. The first stage is formation of HBr, which is a gas, but under the reaction conditions some of the HBr is oxidized by further H2SO4 to form bromine and sulphur dioxide. This reaction does not work with the corresponding chlorides and fluorides.

NaBr (s) + H2SO4 (l) → HBr (g) + NaHSO4 (s)

2HBr (g) + H2SO4 (l) → Br2 (g) + SO2 (g) + 2H2O (l)

Selenium (34)

Selenium can be prepared with either an amorphous or crystalline structure. Crystalline monoclinic selenium is deep red; crystalline hexagonal selenium, the most stable variety, is a metallic grey (see picture above). Elemental selenium is relatively nontoxic and is considered to be an essential trace element. However, hydrogen selenide (H2Se) and other selenium compounds are extremely toxic, and resemble arsenic in their physiological reactions. Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some soils in amounts sufficient to produce serious effects on animals feeding on plants such as locoweed (an American plant) grown in such soils.

•Name: Selenium
•Symbol: Se
•Atomic number: 34
•Atomic weight: 78.96 (3)
•Standard state: solid at 298 K
•CAS Registry ID: 7782-49-2
•Group in periodic table: 16
•Group name: Chalcogen
•Period in periodic table: 4
•Block in periodic table: p-block
•Color: grey, metallic luster
•Classification: Non-metallic

Historical information

Selenium was discovered by Jöns Berzelius at 1817 in Sweden. Origin of name is from the Greek word "selene" meaning "moon". Selenium (Greek- Selen, moon) was discovered by Jöns Jacob Berzelius in 1817. He reported that tellurium was present in sulphuric acid from a Swedish factory, but in the following year decided that the impurity was not tellurium but another closely related element that he subsequently identified as selenium.

Physical properties

•Melting point: 494 [or 221 °C (430 °F)] K
•Boiling point: 958 [or 685 °C (1265 °F)] K
•Density of solid: 4819 kg m-3

Orbital properties

•Ground state electron configuration: [Ar].3d10.4s2.4p4
•Shell structure: 2.8.18.6
•Term symbol: 3P2

Isolation

It is not usually necessary to make selenium in the laboratory as it is commercially available. While there are several selenium ores, most selenium is made as a byproduct of copper refining. It also accumulates in the residues from sulphuric acid manufacture. Extraction is complex since the method employed will depend upon what other compounds or elements are present. The first step usually involves an oxidation in the presence of sodium carbonate (soda ash).

Cu2Se + Na2CO3 + 2O2 → 2CuO + Na2SeO3 + CO2

The selenite Na2SeO3 is acidified with sulphuric acid. Any tellurites precipitate out leaving selenous acid, H2SeO3, in solution. Selenium is liberated from selenous acid by SO2:

H2SeO3 + 2SO2 + H2O → Se + H2SO4 (concentrated)