Platinum

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78 iridiumplatinumgold
Pd

Pt

Ds
Pt-TableImage.png
periodic table
General
Name, Symbol, Number platinum, Pt, 78
Chemical series transition metals
Group, Period, Block 10, 6, d
Appearance grayish white
Pt,78.jpg
Atomic mass 195.084(9) g/mol
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/cm³
Liquid density at m.p. 19.77 g/cm³
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
Heat of vaporization 469 kJ/mol
Heat capacity (25 °C) 25.86 J/(mol·K)
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 2, 3, 4
(mildly basic oxide)
Electronegativity 2.28 (Pauling scale)
Ionization energies 1st: 870 kJ/mol
2nd: 1791 kJ/mol
Atomic radius 135 pm
Atomic radius (calc.) 177 pm
Covalent radius 128 pm
Van der Waals radius 175 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 105 nΩ·m
Thermal conductivity (300 K) 71.6 W/(m·K)
Thermal expansion (25 °C) 8.8 µm/(m·K)
Speed of sound (thin rod) (r.t.) 2800 m/s
Speed of sound (thin rod) (r.t.) 168 m/s
Shear modulus 61 GPa
Bulk modulus 230 GPa
Poisson ratio 0.38
Mohs hardness 3.5
Vickers hardness 549 MPa
Brinell hardness 392 MPa
CAS registry number 7440-06-4
Notable isotopes
Main article: Isotopes of platinum
iso NA half-life DM DE (MeV) DP
190Pt 0.01% 6.5×1011 y α 3.18 186Os
191Pt syn 2.96 d ε ? 191Ir
192Pt 0.79% Pt is stable with 114 neutrons
193mPt syn 4.33 d IT 0.1355e 193Pt
193Pt syn 50 y ε ? 193Ir
194Pt 32.9% Pt is stable with 116 neutrons
195mPt syn 4.02 d IT 0.1297e 195Pt
195Pt 33.8% Pt is stable with 117 neutrons
196Pt 25.3% Pt is stable with 118 neutrons
197mPt syn 1.59 h IT 0.3465 197Pt
197Pt syn 19.8913 h β- 0.719 197Au
198Pt 7.2% Pt is stable with 120 neutrons

Platinum (chemical symbol Pt, atomic number 78) is a silvery grey precious metal, with a monetary value that is higher than that of gold. Highly resistant to corrosion, it is used in jewelry, laboratory equipment, electrical contacts, dentistry, and automobile emissions control devices.

Developing: 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. ---- Developing.

History

Naturally occurring platinum appears to have been used by the craftsmen of ancient Egypt. Native inhabitants of parts of South America also used it for jewelry long before the arrival of Europeans. The first European account of platinum can be found in the writings of the Italian humanist Julius Caesar Scaliger (1484-1558). In 1557, Scaliger described it as a mysterious metal occurring in Central American mines between Darién (Panama) and Mexico, noting that it could not be melted by any fire or any of the Spanish techniques.

Toward the end of the seventeenth century, when the Spanish conquistadors were looking for gold in the region that is now Colombia, they found silvery beads that they called "platina," or little silver. The metal also came to be called "platina del Pinto," meaning silvery beads from the Pinto River (in Colombia). Details about the metal were recorded by Spanish astronomer Antonio de Ulloa and Don Jorge Juan y Santacilia, both appointed by King Philip V to join a geographical expedition in Peru that lasted from 1735 to 1745. Among other things, de Ulloa observed platina del Pinto to be an "unworkable" metal found with gold in New Granada (Colombia).

On de Ulloa's return voyage, British privateers attacked his ship, which was then handed over to the British navy. De Ulloa was forced to remain in London and his papers were confiscated. Fortunately, the Royal Society received him well, making him a Fellow in 1746. Two years later, he and Juan published their experiences in South America, including a reference to platinum. By then, British scientist Charles Wood had independently obtained the element from Jamaica in 1741. The material was researched by William Brownrigg and William Watson, and Watson reported their findings to the Royal Society in 1750.

Alchemical symbol for platinum

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

Occurrence

Platinum ore

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

In certain areas of the Americas, platinum is often found free or alloyed with iridium as platiniridium. Platinum arsenide (PtAs2), also known as sperrylite, is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. The rare sulfide mineral cooperite contains platinum, palladium, and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex in Transvaal, South Africa. South Africa is the largest producer of platinum in the world.

Often accompanied by small amounts of other platinum family metals (see below), platinum 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 parts per million in the ore.

Notable characteristics

An assortment of native platinum nuggets

Purified platinum has a silvery-white color and an extremely high melting point (3214.9 degrees F). It is also an outstanding catalyst.

Platinum is remarkably resistant to corrosion, including chemical attack by hydrochloric acid and nitric acid. It does not oxidize in air at any temperature. It does, however, dissolve in the mixture of acids known as aqua regia to form chloroplatinic acid. In addition, it can be corroded by cyanides, halogens, sulfur, and caustic alkalis.


Isotopes of platinum

Naturally occurring platinum is composed of five stable isotopes and many radioisotopes. Of these, the radioisotope Pt-190 has a half-life of over 6 billion years, while Pt-193 has a half-life of 50 years.

Platinum family

Six elements in the periodic table are collectively known as the "platinum group" or "platinum family." They are ruthenium, rhodium, palladium, osmium, iridium, and platinum. They have similar physical and chemical properties, and tend to occur together in the same mineral deposits.

Platinum compounds

  • Platinum compounds rarely occur in nature.

Symbolism

Platinum's rarity as a metal has led advertisers to associate it with exclusivity and wealth. "Platinum" credit cards have greater privileges than "gold" ones. "Platinum awards" are the highest possible, ranking above gold, silver, and bronze. A musical album that has sold more than 1,000,000 copies is credited as "platinum." Some products, such as blenders and vehicles with a silvery-white color, are identified as "platinum" (although a higher certification of "diamond" does exist).

Applications

Platinum is considered a precious metal. Being resistant to tarnish and wear, it is well suited for making fine jewelry. Its price changes with availability, but it is usually rated higher than gold.

In the eighteenth century, King Louis XV of France declared platinum the only metal fit for a king. In addition, 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.

For a long time, the definition of a meter was based on the distance between two marks on a bar of a platinum-iridium alloy housed at the Bureau International des Poids et Mesures in Sèvres, France. A platinum-iridium cylinder continues to serve as the standard of the kilogram and is housed in the same facility as the meter bar.


Platinum possesses remarkable resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All these properties have been exploited for industrial applications.


The catalytic properties of the six platinum family metals are outstanding (a mixture of hydrogen and oxygen explodes in the presence of platinum). For this catalytic property, platinum is used in catalytic converters, incorporated in automobile exhaust systems, as well as tips of spark plugs.

  • catalyst utilized in the catalytic converter, an optional component of the gasoline-fueled automobile exhaust system (see "Notable characteristics" in this article),
  • certain platinum-containing compounds are capable of intercalating into DNA and are chemotherapeutic agents owing to this capability. For example, cisplatin, carboplatin and oxaliplatin belong to this class of drugs,
  • platinum resistance thermometers,
  • electrodes for use in electrolysis.

Precautions

Being an unreactive metal, platinum normally does not cause health problems. 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, though they also cause cumulative, irreversible kidney damage.

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See also

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