|Name, Symbol, Number||Platinum, Pt, 78|
|Chemical series||transition metals|
|Group, Period, Block||10, 6, d|
|Density, Mohs hardness scale>Hardness||kg/m³, 3.5|
|Atomic radius (calc.)||pm|
|Covalent radius||128 pm|
|van der Waals radius||175 pm|
|e- 's per energy level||2, 8, 18, 32, 17, 1|
|Oxidation states (Oxide)||4 (mildly Base (chemistry)>basic)|
|Crystal structure||Cubic face centered|
|State of matter||__)|
|Melting point||K (3214.9 °F)|
|Boiling point||4098 K (6917 °F)|
|Molar volume||×10-6 m³/mol|
|Heat of vaporization||kJ/mol|
|Heat of fusion||19.6 kJ/mol|
|Vapor pressure||Pa at 2045 K|
|Speed of sound||m/s at 293.15 K|
|Electronegativity||2.28 (Pauling scale)|
|Specific heat capacity||J/(kg·K)|
|Electrical conductivity||09.66 106/m ohm|
|1st ionization potential||870 kJ/mol|
|2nd ionization potential||1791 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
Platinum is a chemical element in the periodic table that has the symbol Pt and atomic number 78. A heavy, malleable, ductile, precious, gray-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 anti-pollution devices in automobiles.
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The metal is a beautiful silvery-white when pure, and malleable and ductile. The metal is corrosion-resistant. The catalytic properties of the six platinum family metals are outstanding (a mixture of hydrogen and oxygen explodes in the presence of platinum). Platinum's wear- and tarnish-resistance characteristics are well-suited for making fine jewelry.
Other distinctive properties include 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 when mixed as aqua regia (forming chloroplatinic acid). Common oxidation states of platinum include +2, +3, and +4.
Platinum is used extensively in jewelry, wire, in making crucibles for chemical use and for constructing high-temperature electric furnaces. Finely divided platinum is often used as a chemical catalyst. For example, platinum is used in catalytic converters for automobiles and in various industrial processes, such as the manufacture of sulfuric acid. Other uses:
- The metal can absorb large quantities of hydrogen gas and will release it when heated. It is therefore been studied as a possible storage medium for the gas for use in fuel cell vehicles.
- The chemical industry uses a significant amount of either platinum or a platinum-rhodium alloy catalyst in the form of gauze to catalyze the partial oxidation of ammonia to yield nitric oxide, which is the raw material for fertilizers, explosives, and nitric acid.
- Platinum-supported catalysts are used in the refining of crude oil, reforming, and other processes used in the production of high-octane gasoline and aromatic compounds for the petrochemical industry.
- This metal has a coefficient of expansion that is almost equal to that of soda-lime-silica glass and is therefore used to make sealed electrodes in glass systems.
- Alloys of platinum and cobalt have excellent magnetic properties. One alloy that has 76.7% Pt and 23.3% Co, by mass, forms an extremely powerful magnet.
- 90/10 Platinum/osmium alloy is used to make pacemakerss, replacement valves and other surgical implants.
- Used for coating missile nose cones, jet engine fuel nozzles, and other devices which must perform reliably at high temperatures for extended periods of time.
- Fine platinum wire glows red hot when exposed to methyl alcohol vapor acting as a catalyst that converts the alcohol to formaldehyde. This phenomenon has been commercially used to make cigarette lighters and hand warmers.
- Cis-platin, [PtCl2(NH3)2], is a drug that is effective in treating certain types of cancer which include leukemia and testicular cancer.
HistoryThe name platinum derives from the Spanish platina meaning "little silver".
Naturally-occurring platinum and platinum-rich alloys have been known for a long time. Though the metal was used by pre-Columbian Indians, 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 Spaniards named the metal "platina," or little silver, when they first encountered it in Colombia. They regarded platinum as an unwanted impurity in the silver they were mining, and often discarded it.
Platinum was discovered by astronomer Antonio de Ulloa and Don Jorge Juan y Santacilia (1713-1773), 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.
Platinum is now considered more precious than gold, so that a platinum award is better than a golden one. The price of platinum changes along with its availability, but normally it costs up to 8 times as much as gold.
The standard definition of a metre for a long time was based on the distance between two marks on a bar of platinum-iridium housed in Sevres. This metal is also used in the definition of the Standard Hydrogen Electrode.
Platinum is often found in a native state and the ore sperrylite (platinum arsenide, PtAs2) is a major source of the metal. A naturally occurring platinum/iridium alloy is platiniridium and this metal is also found in the mineral cooperite (platinum sulfide, PtS).
Platinum is produced commercially as a by-product of nickel ore processing. The huge quantities of nickel ore processed makes up for the fact that platinum makes up only two parts per million of the ore.
Naturally occurring platinum is composed of five stable isotopes and one radioisotope, Pt-190, which has a very long half-life (over 6 billion years). There are also many other radioisotopes with the most stable being Pt-193 with a half-life of 50 years.
This metal doesn't normally cause health problems due to its unreactive nature but all compounds of platinum should be considered to be highly toxic.
Platinum compounds rarely occur in nature.
In the popular music industry, Platinum is a certification by the RIAA for one million units shipped. For more information see: RIAA certification