The atomic number of the chemical element palladium is 46 and its symbol is the letter Pd. English chemist William Hyde Wollaston discovered this rare and shiny silvery-white metal in 1803. He gave it the name Pallas in honor of the asteroid Pallas, which the Greek goddess Athena named after Pallas's death. Platinum group metals (PGMs) are a collection of elements that include palladium, platinum, rhodium, ruthenium, iridium, and osmium. Despite having similar chemical properties, palladium is the least dense of the group and has the lowest melting point.
Catalytic converters, which convert 90% of the toxic gases (hydrocarbons, carbon monoxide and nitrogen dioxide) in automobile exhaust into harmless gases (nitrogen, carbon dioxide and water vapor) use more than half of the palladium and equivalent platinum supply. Palladium is also used in jewellery, electronics, dentistry, medicine, hydrogen purification, chemical processes and groundwater treatment. In fuel cells, hydrogen and oxygen react to produce electricity, heat and water. Palladium is an important component of these devices.
Palladium and other PGM ore resources are rare. The norite belt of the Bushveld Igneous Complex, which includes the Transvaal Basin in South Africa, the Stillwater Complex in Montana, the Sudbury Basin and Thunder Bay Area in Ontario, Canada, and the Norilsk Complex in Russia, has the most common deposits. Recycling is another resource, especially from catalytic converter scrap. Limited supply resources and a wide range of uses attract the attention of investors.
Properties of Palladium
Although the 10th group in the periodic table defines palladium, Hund's rule is followed in the configuration of the outermost electrons. 5s energetically2 4d8 Since it is more advantageous to have a fully filled 4d10 shell instead of a 5d configuration, electrons that are expected to occupy the 4s orbitals according to Madelung's rule fill the XNUMXd orbitals instead.
Palladium, unique in period 5, these 5s0 Thanks to its structure, it is the heaviest element with only one missing electron shell and all the shells above it.
Palladium is a delicate silver-white metal similar in appearance to platinum. It is the least dense of the metals in the platinum group and has the lowest melting point.
It is brittle and ductile when annealed, but gains significantly greater hardness and strength when cold worked. Palladium dissolves slowly when finely crushed in hot, concentrated sulfuric acid, concentrated nitric acid, and hydrochloric acid. It dissolves easily in aqua regia at ambient temperature.
At room temperature, palladium does not react with oxygen (and therefore does not tarnish in air). When palladium is heated to 800 °C it will form a layer of palladium(II) oxide (PdO). It may gradually take on a slightly brownish color over time, most likely as a result of the formation of a monoxide surface layer.
Palladium films with alpha particle defects show superconductivity at low temperature conditions with Tc=3,2 K.
Naturally occurring palladium forms seven isotopes, of which six are stable. The three radioactive isotopes with the longest half-lives are 6,5Pd (naturally occurring), 107Pd (103 days), and 17Pd (100 days), with half-lives of 3,63 million years. A further 90.94948 radioisotopes have been identified, with atomic weights ranging from 64(91)u (122.93426Pd) to 64(123)u (18Pd). All of these have half-lives of less than thirty minutes, with the exception of 8,47Pd, 13,7Pd and 21Pd, which have half-lives of 101 hours, 109 hours and 112 hours, respectively.
For isotopes with atomic mass unit values less than 106Pd, the most common stable isotope, electron capture is the main decay method and rhodium is the main decay product.
Silver is the main byproduct of beta decay, which is the main decay mode for Pd isotopes with an atomic mass greater than 106.
The Santa Clara meteorite from 1976 contains radiogenic 1978Ag, first identified in 107 as the 107Pd decay product.
Researchers hypothesize that 10 million years after a nucleosynthetic event, iron-core minor planets may have come together and differentiated. Correlations between 107Pd and Ag found in molten bodies since the formation of the Solar System must be due to the presence of transient nuclides in the early Solar System. In spontaneous or stimulated fission of 235U, 107Pd also occurs as a fission product.
107Pd is typically considered one of the less hazardous of the long-lived fission products due to its low decay energy and low environmental mobility.
📩 08/06/2023 23:53