Platinum is a chemical element; it has symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish platina, a diminutive of plata "silver". Platinum is a member of the platinum group of elements and group 10 of the periodic table of elements. It has six naturally occurring isotopes. It is one of the rarer elements in Earth's crust, with an average abundance of approximately 5 μg/kg. It occurs in some nickel and copper ores along with some native deposits. Because of its scarcity in Earth's crust, barely a few hundred metric tonnes are produced annually, and given its critical and important uses, it is highly valuable as well as a major precious metal commodity. Platinum does not corrode, even at high temperatures, and is therefore considered a noble metal. Consequently, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the alluvial sands of various rivers, it was first used by pre-Columbian South American natives to produce artifacts. It was referenced in European writings as early as the 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it began to be understood by scientists. Platinum is a key component in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Platinum is also used in the glass industry to manipulate molten glass, which does not "wet" platinum. Compounds containing platinum, such as cisplatin, oxaliplatin and carboplatin, are applied in chemotherapy as treatment for certain types of cancer.
Characteristics
Physical Platinum is a lustrous, ductile, and malleable, silver-white metal. Platinum is more ductile than gold, silver or copper, thus being the most ductile of pure metals. Its physical characteristics and chemical stability make it useful for industrial applications. Its resistance to wear and tarnish is well suited to use in fine jewelry.
Chemical
Platinum does not corrode, and bulk platinum does not oxidize in air at any temperature, but heated metal wires lose weight faster in air or oxygen than it does in a vacuum. The suggestion is that Pt forms a thin surface film of PtO2 that decomposes when heated above 500 °C. The most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. Tetracoordinate platinum(II) compounds tend to adopt 16-electron square planar geometries. Although elemental platinum is generally unreactive, it is attacked by chlorine, bromine, iodine, and sulfur. It reacts vigorously with fluorine at 500 °C (932 °F) to form platinum tetrafluoride. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot aqua regia (a mixture of nitric and hydrochloric acids), to form aqueous chloroplatinic acid, H2PtCl6:
Pt + 4 HNO3 + 6 HCl → H2PtCl6 + 4 NO2 + 4 H2O As a soft acid, the Pt2+ ion has a great affinity for sulfide and sulfur ligands. Numerous DMSO complexes have been reported and care is taken in the choosing of reaction solvents. In 2007, the German scientist Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum (catalytic converter).
Isotopes
Platinum has six naturally occurring isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt. The most abundant of these is 195Pt, comprising 33.83 % of all platinum; it is the only stable isotope with a non-zero spin, of ½, and it is favorable for use in 195Pt NMR. Due to its spin and large abundance, 195Pt satellite peaks are also often observed in 1H and 31P NMR spectroscopy (e.g., for Pt-phosphine and Pt-alkyl complexes). The radioactive 190Pt is the least abundant of these at only 0.012 %; it undergoes alpha decay with a half-life of 4.83×1011 years, causing the very low activity of 16.8 Bq/kg of natural platinum. The decay of this isotope has some use in isotope geology, though not directly for dating. The other natural isotopes are theoretically capable of alpha decay also, but this has never been observed, and therefore they are considered stable. Platinum also has 38 synthetic isotopes ranging in atomic mass from 165 to 208, making the total number of known isotopes 44. The most stable of these radioisotopes is 193Pt, with a half-life of 50 years. Most platinum isotopes decay by some combination of beta decay and (on the proton-rich side) alpha decay. 188Pt, 191Pt, and 193Pt decay only by electron capture (besides the very small alpha branch of the first). 190Pt and 198Pt are predicted to have energetically favorable double beta decay paths.
Occurrence
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