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78 iridiumplatinumgold


Name, Symbol, Number platinum, Pt, 78
Chemical series transition metals
Group, Period, Block 10, 6, d
Appearance grayish white
Standard atomic weight 195.084(9)  g·mol−1
Electron configuration [Xe] 4f14 5d9 6s1
Electrons per shell 2, 8, 18, 32, 17, 1
Physical properties
Phase solid
Density (near r.t.) 21.45  g·cm−3
Liquid density at m.p. 19.77  g·cm−3
Melting point 2041.4 K
(1768.3 °C, 3214.9 °F)
Boiling point 4098 K
(3825 °C, 6917 °F)
Heat of fusion 22.17  kJ·mol−1
Heat of vaporization 469  kJ·mol−1
Heat capacity (25 °C) 25.86  J·mol−1·K−1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 2330 (2550) 2815 3143 3556 4094
Atomic properties
Crystal structure cubic face centered
Oxidation states 1, 2, 3, 4, 5, 6
(mildly basic oxide)
Electronegativity 2.28 (Pauling scale)
Ionization energies 1st: 870 kJ/mol
2nd: 1791 kJ/mol
Atomic radius 135pm
Atomic radius (calc.) 177  pm
Covalent radius 128  pm
Van der Waals radius 175 pm
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 105 n Ω·m
Thermal conductivity (300 K) 71.6  W·m−1·K−1
Thermal expansion (25 °C) 8.8  µm·m−1·K−1
Speed of sound (thin rod) (r.t.) 2800  m·s−1
Young's modulus 168  GPa
Shear modulus 61  GPa
Bulk modulus 230  GPa
Poisson ratio 0.38
Mohs hardness 4 - 4.5
Vickers hardness 549  MPa
Brinell hardness 392  MPa
CAS registry number 7440-06-4
Selected isotopes
Main article: Isotopes of platinum
iso NA half-life DM DE (MeV) DP
190Pt 0.014% 6.5×1011 y α 3.18 186Os
191Pt syn 2.96 d ε  ? 191Ir
192Pt 0.782% Pt is stable with 114 neutrons
193Pt syn 50 y ε  ? 193Ir
193mPt syn 4.33 d IT 0.1355e 193Pt
194Pt 32.967% Pt is stable with 116 neutrons
195Pt 33.832% Pt is stable with 117 neutrons
195mPt syn 4.02 d IT 0.1297e 195Pt
196Pt 25.242% Pt is stable with 118 neutrons
197Pt syn 19.8913 h β- 0.719 197Au
197mPt syn 1.59 h IT 0.3465 197Pt
198Pt 7.163% Pt is stable with 120 neutrons

This page is about platinum the chemical element. For other uses, see Platinum (disambiguation).

Platinum (IPA: /ˈplætɪnəm/) is a chemical element in the periodic table that has the symbol Pt and atomic number 78. A heavy, malleable, ductile, precious, grey-white transition metal, platinum is resistant to corrosion and occurs in some nickel and copper ores along with some native deposits. Platinum is used in jewelry, laboratory equipment, electrical contacts, dentistry, and automobile emissions control devices.


[edit] Notable characteristics

An assortment of native platinum nuggets
An assortment of native platinum nuggets

When pure, the metal appears greyish-white and firm. The metal is corrosion-resistant. The catalytic properties of the six platinum family metals are outstanding. For this catalytic property, platinum is used in catalytic converters, incorporated in automobile exhaust systems, as well as tips of spark plugs.

Platinum's wear- and tarnish-resistance characteristics are well suited for making fine jewelry. Platinum is more precious than gold. The price of platinum changes along with its availability, but it normally costs slightly less than twice the price of gold. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king.[1]

Platinum possesses high resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications. Platinum does not oxidize in air at any temperature, but can be corroded by cyanides, halogens, sulfur, and caustic alkalis. This metal is insoluble in hydrochloric and nitric acid, but does dissolve in the mixture known as aqua regia (forming chloroplatinic acid). Common oxidation states of platinum include +2, and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal metal bonding in bimetallic (or polymetallic) species.

[edit] Applications

better if alloyed with rhodium (10-40% of Rh).

[edit] History

Naturally-occurring platinum and platinum-rich alloys have been known for a long time. Though the metal was used by pre-Columbian Native Americans, the first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger (1484-1558) as a description of a mysterious metal found in Central American mines between Darién (Panama) and Mexico ("up until now impossible to melt by any of the Spanish arts"). The word platinum comes from the Spanish word platina, meaning "little silver."

Platinum was discussed by astronomer Antonio de Ulloa and Don Jorge Juan y Santacilia (17131773), both appointed by King Philip V to join a geographical expedition in Peru that lasted from 1735 to 1745. Among other things, Ulloa observed the platina del pinto, the unworkable metal found with gold in New Granada (Colombia). British privateers intercepted Ulloa's ship on the return voyage. Though he was well-treated in England, and even made a member of the Royal Society he was prevented from publishing a reference to the unknown metal until 1748. Before that could happen Charles Wood independently isolated the element in 1741.

Alchemical symbol for platinum

The alchemical symbol for platinum (shown left) was made by joining the symbols of silver and gold.

[edit] Occurrence

Platinum ore
Platinum ore

Platinum is an extremely rare metal, occurring as only 5 ppb in the Earth's crust.

Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. The platinum arsenide, sperrylite (PtAs2), is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex, Transvaal, South Africa. South Africa is the largest producer of platinum in the world.

Platinum, often accompanied by small amounts of other platinum family metals, occurs in alluvial placer deposits in the Witwatersrand of South Africa, Colombia, Ontario, the Ural Mountains, and in certain western American states.

Platinum is produced commercially as a by-product of nickel ore processing in the Sudbury deposit. The huge quantities of nickel ore processed makes up for the fact that platinum is present as only 0.5 ppm in the ore.

[edit] Precautions

According to the Centers for Disease Control and Prevention, short-term exposure to platinum salts "may cause irritation of the eyes, nose, and throat" and long-term exposure "may cause both respiratory and skin allergies." The current OSHA standard is 0.002 milligram per cubic meter of air averaged over an 8-hour work shift.[2]

Certain platinum complexes (cis-platin) have been used in chemotherapy, as they have very good anti-tumor activity, particularly when used to combat testicular cancer,[citation needed] although they also cause cumulative, irreversible kidney damage,[citation needed] as well as deafness.[citation needed]

As platinum is a catalyst in the manufacture of the silicone rubber and gel components of several types of medical implants (breast implants, joint replacement prosthetics, artificial lumbar discs, vascular access ports),[citation needed] the possibility that platinum free radicals could enter the body and cause adverse effects has merited study. However, the FDA has reviewed the issue as related to breast implants, and did not agree with a recent study that showed possible in vivo toxicity.[3]

[edit] Rarity and color

Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" credit cards have greater privileges than do "gold" ones. "Platinum awards" are the second highest possible, ranking above gold, silver and bronze, but below "Diamond". For example, a musical album that has sold more than 1,000,000 copies, will be credited as "platinum." And some products, such as blenders and vehicles, with a silvery-white colour are identified as "platinum". Platinum is considered a precious metal, although its use is not as common as the use of gold or silver. The frame of the Crown of Queen Elizabeth the Queen Mother, manufactured for her Coronation as Consort of King George VI, is made of platinum. It was the first British crown to be made of that metal.

[edit] World production

World supply of platinum is around 7 million troy ounces (199,000 kg) per year.[4][5] Platinum's cost fluctuates around USD $1100 per ounce ($35/g). [2]

[edit] References

  1. ^ Platinum. Minerals Zone. Retrieved on April 5, 2007.
  2. ^ Centers for Disease Control and Prevention
  3. ^ [1]
  4. ^ Johnson Matthey 2006 supply and demand charts
  5. ^ BBC 2002 article on supply and demand

[edit] See also

[edit] External links

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