List of Platinum Group Metals or PGMs

What Are the Platinum Group Metals?

Elements belonging to the platinum group metals all share characteristics with platinum (shown here).
Elements of the platinum group metals all share characteristics with platinum (shown here). Harry Taylor, Getty Images

The platinum group metals or PGMs are a set of six transition metals that share similar properties. They may be considered a subset of the precious metals. The platinum group metals are clustered together on the periodic table, plus these metals tend to be found together in minerals. The list of PGMs is:

Alternate Names: The platinum group metals are also known as: PGMs, platinum group, platinum metals, platinoids, platinum group elements or PGEs, platinides, platidises, platinum family

Key Takeaways: Platinum Group Metals

  • The platinum group metals or PGMs are a set of six precious metals that are clustered together on the periodic table around the element platinum.
  • The elements share certain desirable properties with platinum. All are noble metals and transition metals in the d-block of the periodic table.
  • The platinum group metals are widely used as catalysts, corrosion-resistant materials, and fine jewelry.

Properties of the Platinum Group Metals

The six PGMs share similar properties, including:

  • Extremely high density (densest element is a PGM)
  • Highly resistant to wear or tarnish
  • Resist corrosion or chemical attack
  • Catalytic properties
  • Stable electrical properties
  • Stable at high temperatures

Uses of PGMs

  • Several of the platinum group metals are used in jewelry. In particular, platinum, rhodium, and iridium are popular. Because of the price of these metals, they are often used as coatings over softer, more reactive metals, such as silver.
  • PGMs are important catalysts. Platinum catalysts are important in the petrochemical industry. Platinum or platinum-rhodium alloy are used to catalyze partial oxidation of ammonia to produce nitric oxide, an important raw material in chemical production. PGMS are also used as catalysts for organic chemical reactions. The automotive industry uses platinum, palladium, and rhodium in catalytic converters to treat exhaust emissions.
  • Platinum group metals are used as alloying additives.
  • PGMs may be used to make crucibles used to grow single crystals, particularly of oxides.
  • Platinum group metal alloys are used to make electrical contacts, electrodes, thermocouples, and circuits.
  • Iridium and platinum are used in medical implants and pacemakers.

Sources of Platinum Group Metals

Platinum gets its name from platina, meaning "little silver," because the Spaniards considered it an unwanted impurity in silver mining operations in Colombia. For the most part, PGMs are found together in ores. Ultramafic and mafic igneous rocks contain high levels of platinum group metals, the granites contain a low percentage of the metals. The richest deposits include mafic layered intrusions, such as Bushveld Complex. Platinum metals are found in the Ural Mountains, North and South America, Ontario, and other places. Platinum metals are also produced as a by-product of nickel mining and processing. Additionally, the light platinum group metals (ruthenium, rhodium, palladium) form as fission products in nuclear reactors.

Extraction

Platinum metal extraction processes are typically trade secrets. First, the sample is dissolved in acid. Aqua regia is most often used for this purpose. This produces a solution of metal complexes. Basically, isolation uses the different solubilities and reactivities of the different elements in various solvents. While recovering noble metals from reactors is expensive, the escalating price of the metals has made spent nuclear fuel a viable source of the elements.

History

Platinum and its alloys occur in native form and were known by pre-Columbian Americans. Despite its early use, platinum does not appear in literature until the 16th century. In 1557, Italian Julius Caesar Scalinger wrote of a mysterious metal found in Central America that was unknown to Europeans.

Fun Fact

Iron, nickel, and cobalt are three transition metals located above the platinum group metals on the periodic table. They are the only transition metals that are ferromagnetic!

Sources

  • Kolarik, Zdenek; Renard, Edouard V. (2005). "Potential Applications of Fission Platinoids in Industry." Platinum Metals Review. 49 (2): 79. doi:10.1595/147106705X35263
  • Renner, H.; Schlamp, G.; Kleinwächter, I.; Drost, E.; Lüschow, H. M.; Tews, P.; Panster, P.; Diehl, M.; et al. (2002). "Platinum group metals and compounds". Ullmann's Encyclopedia of Industrial Chemistry. Wiley. doi:10.1002/14356007.a21_075
  • Weeks, M. E. (1968). Discovery of the Elements (7 ed.). Journal of Chemical Education. pp. 385–407. ISBN 0-8486-8579-2.
  • Woods, Ian (2004). The Elements: Platinum. Benchmark Books. ISBN 978-0-7614-1550-3.
  • Xiao, Z.; Laplante, A. R. (2004). "Characterizing and recovering the platinum group minerals—a review." Minerals Engineering. 17 (9–10): 961–979. doi:10.1016/j.mineng.2004.04.001