Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, and highly unreactive precious metal with a silver-white appearance. Its name comes from the Spanish word “platina,” meaning “little silver.”
Platinum belongs to the platinum group of elements and is in group 10 of the periodic table. It has six naturally occurring isotopes and is one of the rarer elements in the Earth’s crust, with an average abundance of about 5 micrograms per kilogram. Most platinum is found in nickel and copper ores, and it is primarily extracted from South Africa, which produces approximately 80% of the world’s platinum. Due to its rarity and essential uses, platinum is a highly valuable precious metal.
Characteristics
- Physical: Pure platinum is a shiny, silver-white metal that is more ductile than gold, silver, or copper, making it the most ductile of pure metals. However, it is less malleable than gold. Platinum’s physical properties and chemical stability make it useful in various industrial applications, including fine jewelry.
- Chemical: Platinum is highly resistant to corrosion and does not oxidize in air at any temperature. It forms a thin surface film of PtO2, which can be removed by heating. The most common oxidation states of platinum are +2 and +4, with less common states being +1 and +3. Platinum reacts with chlorine, bromine, iodine, and sulfur and forms compounds such as platinum tetrafluoride when reacting with fluorine. It is insoluble in hydrochloric and nitric acids but dissolves in hot aqua regia.
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Isotopes
Platinum has six naturally occurring isotopes: 190^{190}190Pt, 192^{192}192Pt, 194^{194}194Pt, 195^{195}195Pt, 196^{196}196Pt, and 198^{198}198Pt. The most abundant isotope is 195^{195}195Pt, which makes up about 33.83% of natural platinum and is the only stable isotope with a non-zero spin. Platinum also has 38 synthetic isotopes with atomic masses ranging from 165 to 208. The most stable of these is 193^{193}193Pt, with a half-life of 50 years.
Occurrence
Platinum is extremely rare, with a concentration of about 0.005 parts per million in the Earth’s crust. It is often found as native platinum or in alloys with other platinum-group metals. Major sources include alluvial deposits in Colombia and the Ural Mountains, as well as nickel and copper deposits in regions like the Sudbury Basin in Canada and Norilsk in Russia. South Africa, in particular, has significant platinum deposits, contributing to about 77% of global production as of 2010.
Compounds
- Halides: Hexachloroplatinic acid is a key platinum compound used as a precursor for other platinum compounds. It has applications in photography, porcelain coloring, and as a catalyst.
- Oxides: Platinum(IV) oxide (PtO2), known as Adams’ catalyst, is a black powder soluble in potassium hydroxide and concentrated acids. Other platinum oxides decompose upon heating.
- Other Compounds: Platinum can exhibit negative oxidation states, forming compounds such as barium platinides and caesium platinide. Cisplatin, a platinum-containing chemotherapy drug, is used to treat various cancers by crosslinking DNA.
History
Platinum was used by pre-Columbian South American natives for artifacts. It was first described in European writings in the 16th century, with Antonio de Ulloa’s 1748 report marking the start of scientific investigation into the metal. Early uses include platinum jewelry and artifacts, with advancements in malleability and purity achieved in the 18th and 19th centuries.
Production
Platinum is primarily obtained as a by-product of nickel and copper mining. It is refined through methods like electrorefining, where it is separated from impurities using techniques such as floating, electromagnetism, and acid treatment. The production of platinum has environmental impacts.
Applications
Platinum is used in catalytic converters, laboratory equipment, electrical contacts, dentistry, and jewelry. It is crucial in the automotive industry for controlling emissions and in fuel cells for green energy technologies. Historically, platinum was used in defining the meter and kilogram standards.
Investment
Platinum is considered a precious metal and is used in jewelry and limited-edition watches. Its price fluctuates based on economic conditions and industrial demand. Historically, platinum has been valued for its rarity and prestige.
Conclusion
Platinum is a versatile and valuable metal with unique physical and chemical properties. It plays a critical role in various industrial applications, including catalysts, electronics, and jewelry. Its rarity and value have made it a symbol of prestige and an important commodity in global markets.
