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Palladium (Pd)

QUICK REFERENCE

  • Symbol: Pd
  • Atomic Number: 46
  • Atomic Weight: 106.42
  • Element Classification: Transition Metal
  • Discovered By: William Hyde Wollaston
  • Discovery Date: 1803
  • Name Origin: Named after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas
  • Density(g/cc): 12.023
  • Melting Point: 1554.9°C
  • Boiling Point: 2963°C
  • Appearance: Silvery-white, lustrous metal
  • Atomic Radius(pm): 169

Discovery

Palladium was discovered by English chemist William Hyde Wollaston in 1803 while he was working on platinum ores. Wollaston dissolved the ore in aqua regia (a mixture of hydrochloric and nitric acids), neutralized the solution with sodium hydroxide, and then precipitated the platinum with ammonium chloride. In the course of these experiments, he found a new metal, palladium, which he sold anonymously at first. He named the element after the asteroid Pallas, which had been discovered two years earlier.

Relation to Other Elements

Palladium is a member of the platinum group metals (PGMs), which also includes platinum, rhodium, ruthenium, osmium, and iridium. These metals are characterized by their remarkable resistance to corrosion and oxidation, as well as excellent catalytic properties. Palladium is unique among PGMs for its ability to absorb hydrogen, up to 900 times its own volume, a property that is exploited in various applications. It is primarily found in the +2 and +4 oxidation states in its compounds.

Natural Occurrence

Palladium is found in the Earth’s crust in rare deposits and is often obtained as a byproduct of nickel and copper mining and processing. The largest palladium supplies come from Russia, South Africa, Canada, and the United States. Natural palladium can also be found alloyed with gold and other platinum-group metals in placer deposits.

Uses

Palladium has a wide range of applications, highlighting its versatility:

  • Catalysis: Palladium is extensively used as a catalyst in the chemical industry, including in catalytic converters in automobiles to reduce harmful emissions, in hydrogenation and dehydrogenation reactions, and in the Heck reaction in organic synthesis.
  • Jewelry: Palladium is used in jewelry, often as an alloy with gold to produce “white gold.” It is also used in its pure form for rings, watches, and other fine jewelry due to its natural white lustrous appearance and resistance to tarnishing.
  • Electronics: Palladium is utilized in the manufacture of electronic components, including connectors and capacitors, because of its good conductivity and durability.
  • Dentistry: Palladium alloys are used in dental fillings and crowns because of their strength and biocompatibility.
  • Fuel Cells: Palladium’s ability to absorb hydrogen makes it valuable in fuel cells, where it acts as an electrode material to catalyze the reaction of hydrogen and oxygen to produce electricity, water, and heat.

The discovery of palladium not only expanded the set of tools available for chemists and engineers but also introduced a metal crucial for environmental protection through its use in catalytic converters. Its unique properties and applications underline the importance of palladium in modern technology and sustainable energy solutions.

 

Ruthenium (Ru)

Silver (Ag)