Palladium: Difference between revisions

Palladium, ₄₆Pd
Palladium
Pronunciation	/pəˈleɪdiəm/ (pə-LAY-dee-əm)
Appearance	silvery white
Standard atomic weight Ar°(Pd)
	106.42±0.01; 106.42±0.01 (abridged);
Palladium in the periodic table
	rhodium ← palladium → silver
Atomic number (Z)	46
Group	group 10
Period	period 5
Block	d-block
Electron configuration	[Kr] 4d10
Electrons per shell	2, 8, 18, 18
Physical properties
Phase at STP	solid
Melting point	1828.05 K (1554.9 °C, 2830.82 °F)
Boiling point	3236 K (2963 °C, 5365 °F)
Density (at 20° C)	12.007 g/cm3
when liquid (at m.p.)	10.38 g/cm3
Heat of fusion	16.74 kJ/mol
Heat of vaporization	358 kJ/mol
Molar heat capacity	25.98 J/(mol·K)
Atomic properties
Oxidation states	0, +1, +2, +3, +4, +5 (a mildly basic oxide)
Electronegativity	Pauling scale: 2.20
Ionization energies	1st: 804.4 kJ/mol ; 2nd: 1870 kJ/mol ; 3rd: 3177 kJ/mol ; ;
Atomic radius	empirical: 137 pm
Covalent radius	139±6 pm
Van der Waals radius	163 pm
	Spectral lines of palladium
Other properties
Natural occurrence	primordial
Crystal structure	face-centered cubic (fcc) (cF4)
Lattice constant	a = 389.02 pm (at 20 °C)
Thermal expansion	11.77×10−6/K (at 20 °C)
Thermal conductivity	71.8 W/(m⋅K)
Electrical resistivity	105.4 nΩ⋅m (at 20 °C)
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+567.4×10−6 cm3/mol (288 K)
Young's modulus	121 GPa
Shear modulus	44 GPa
Bulk modulus	180 GPa
Speed of sound thin rod	3070 m/s (at 20 °C)
Poisson ratio	0.39
Mohs hardness	4.75
Vickers hardness	400–600 MPa
Brinell hardness	320–610 MPa
CAS Number	7440-05-3
History
Naming	after asteroid Pallas, itself named after Pallas Athena
Discovery and first isolation	William Hyde Wollaston (1802)
Isotopes of palladium v; e;
γ	–
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Palladium (Template:Pron-en, pə-LAY-dee-əm) is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas.

Palladium, along with platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). Platinum group metals share similar chemical properties, but palladium has the lowest melting point and is the least dense of these precious metals.

The unique properties of palladium and other platinum group metals account for their widespread use. One in four goods manufactured today either contain platinum group metals or had platinum group metals play a key role during their manufacturing process.^[8] Over half of the supply of palladium and its congener platinum goes into catalytic converters, which convert up to 90% of harmful gases from auto exhaust (hydrocarbons, carbon monoxide and nitrogen oxide) into less harmful substances (nitrogen, carbon dioxide and water vapor). Palladium is found in many electronics including computers, mobile phones, multi-layer ceramic capacitors, component plating, low voltage electrical contacts, and SED/OLED/LCD televisions. Palladium is also used in dentistry, medicine, hydrogen purification, chemical applications, and groundwater treatment. Palladium plays a key role in the technology used for fuel cells, which combines hydrogen and oxygen to produce electricity, heat and water.

Ore deposits of palladium and other platinum group metals are rare, and the most extensive deposits have been found in the norite belt of the Bushveld Igneous Complex in the Transvaal in South Africa, the Stillwater Complex in Montana, United States, the Sudbury District of Ontario, Canada, and the Norilsk Complex in Russia. In addition to mining, recycling is also a source of palladium, mostly from scrapped catalytic converters. The numerous applications and limited supply sources of palladium result in palladium drawing considerable investment interest.

History

Palladium was discovered by William Hyde Wollaston in 1803.^[9]^[10] This element was named by Wollaston in 1804 after the asteroid Pallas, which had been discovered two years earlier.^[11] Wollaston found palladium in crude platinum ore from South America by dissolving the ore in aqua regia, neutralizing the solution with sodium hydroxide, and precipitating platinum as ammonium chloroplatinate with ammonium chloride. He added mercuric cyanide to form the compound palladium cyanide, which was heated to extract palladium metal.

Palladium chloride was at one time prescribed as a tuberculosis treatment at the rate of 0.065 g per day (approximately one milligram per kilogram of body weight). This treatment did have many negative side-effects, and was later replaced by more effective drugs.^[12]

Palladium's affinity for hydrogen led it to play an essential role in the Fleischmann-Pons experiment in 1989, also known as cold fusion.

In the run up to 2000, Russian supply of palladium to the global market was repeatedly delayed and disrupted^[13] because the export quota was not granted on time, for political reasons. The ensuing market panic drove the palladium price to an all-time high of $1100 per troy ounce in January 2001.^[14] Around this time, the Ford Motor Company, fearing auto vehicle production disruption due to a possible palladium shortage, stockpiled large amounts of the metal purchased near the price high. When prices fell in early 2001, Ford lost nearly US$1 billion.^[15] World demand for palladium increased from 100 tons in 1990 to nearly 300 tons in 2000. The global production of palladium from mines was 222 metric tons in 2006 according to USGS data.^[16] Most palladium is used for catalytic converters in the automobile industry.^[17]

Occurrence

In 2005, Russia was the top producer of palladium, with at least 50% world share, followed by South Africa, Canada and the U.S., reports the British Geological Survey.

Palladium may be found as a free metal alloyed with gold and other platinum group metals in placer deposits of the Ural Mountains, Australia, Ethiopia, South and North America. It is commercially produced from nickel-copper deposits found in South Africa, Ontario, and Siberia; It takes processing of many metric tons of ore to extract just one troy ounce of palladium. However, the mine production could still be profitable, depending on current metal prices, as other metals are produced together: nickel, copper, platinum and rhodium.

The world's largest single producer of palladium is MMC Norilsk Nickel produced from the Norilsk–Talnakh nickel deposits. The Merensky Reef of the Bushveld Igneous Complex of South Africa contains significant palladium in addition to other platinum group elements. The Stillwater igneous complex of Montana and the Roby zone orebody of the Lac des Îles igneous complex of Ontario also contain mineable palladium.

Palladium is also produced in nuclear fission reactors and can be extracted from spent nuclear fuel (see synthesis of noble metals) though the quantity produced is insignificant.

Palladium is found in the rare minerals cooperite and polarite.

Characteristics

Palladium belongs to group 10 in the periodic table:

Z	Element	No. of electrons/shell
28	nickel	2, 8, 16, 2
46	palladium	2, 8, 18, 18
78	platinum	2, 8, 18, 32, 17, 1
110	darmstadtium	2, 8, 18, 32, 32, 17, 1

but has a very atypical configuration in its outermost electron shells compared to the rest of the members of group 10, if not to all elements. (See also niobium (41), ruthenium (44), and rhodium (45).)

Palladium is a soft silver-white metal that resembles platinum. It is the least dense and has the lowest melting point of the platinum group metals. It is soft and ductile when annealed and greatly increases its strength and hardness when it is cold-worked. Palladium dissolves slowly in sulfuric, nitric, and hydrochloric acid.^[11] This metal also does not react with oxygen at normal temperatures (and thus does not tarnish in air). Palladium heated to 800°C will produce a layer of palladium(II) oxide (PdO). It lightly tarnishes in moist atmosphere containing sulfur.

The metal has the uncommon ability to absorb up to 900 times its own volume of hydrogen at room temperatures. It is thought that this possibly forms palladium hydride (PdH₂) but it is not yet clear if this is a true chemical compound.^[11] When palladium has absorbed large amounts of hydrogen, it will expand slightly in size.^[18]

Common oxidation states of palladium are 0,+1, +2 and +4. Although originally +3 was thought of as one of the fundamental oxidation states of palladium, there is no evidence for palladium occurring in the +3 oxidation state; this has been investigated via X-ray diffraction for a number of compounds, indicating a dimer of palladium(II) and palladium(IV) instead. Recently, compounds with an oxidation state of +6 were synthesised.

Isotopes

Naturally-occurring palladium is composed of six isotopes. The most stable radioisotopes are ¹⁰⁷Pd with a half-life of 6.5 million years, ¹⁰³Pd with a half-life of 17 days, and ¹⁰⁰Pd with a half-life of 3.63 days. Eighteen other radioisotopes have been characterized with atomic weights ranging from 90.94948(64) u (⁹¹Pd) to 122.93426(64) u (¹²³Pd).^[19] Most of these have half-lives that are less than a half-hour, except ¹⁰¹Pd (half-life: 8.47 hours), ¹⁰⁹Pd (half-life: 13.7 hours), and ¹¹²Pd (half-life: 21 hours).

The primary decay mode before the most abundant stable isotope, ¹⁰⁶Pd, is electron capture and the primary mode after is beta decay. The primary decay product before ¹⁰⁶Pd is rhodium and the primary product after is silver.

Radiogenic ¹⁰⁷Ag is a decay product of ¹⁰⁷Pd and was first discovered in the Santa Clara, California meteorite of 1978.^[20] The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. ¹⁰⁷Pd versus Ag correlations observed in bodies, which have clearly been melted since accretion of the solar system, must reflect the presence of short-lived nuclides in the early solar system.^[21]

Compounds

Palladium(II) chloride, bromide and acetate are reactive and relatively inexpensive, making them convenient entry points to palladium chemistry. All three compounds are not monomeric; the chloride and bromide often need to be refluxed in acetonitrile to obtain the more reactive acetonitrile complex monomers, e.g.:^[22]

PdCl₂ + 2 MeCN → PdCl₂(MeCN)₂

The great many reactions in which palladium compounds serve as catalysts are collectively known as palladium coupling reactions. Prominent examples include the Heck, Suzuki reaction, and Stille reactions. Palladium(II) acetate, tetrakis(triphenylphosphine)palladium(0) (Pd(PPh₃), and tris(dibenzylideneacetone)dipalladium(0) (Pd₂(dba)₃) are useful in this regard, either as catalysts, or as starting points to catalysts.

Applications

The largest use of palladium today is in catalytic converters.^[23] Palladium is also used in jewelry, in dentistry,^[23]^[24] watch making, in blood sugar test strips, in aircraft spark plugs and in the production of surgical instruments and electrical contacts.^[25] Palladium is also used to make professional transverse flutes.^[26] As a commodity, palladium bullion has ISO currency codes of XPD and 964. Palladium is one of only four metals to have such codes, the others being gold, silver and platinum.

Catalysis

When it is finely divided, such as in palladium on carbon, palladium forms a versatile catalyst and speeds up hydrogenation and dehydrogenation reactions, as well as in petroleum cracking. A large number of carbon-carbon bond forming reactions in organic chemistry (such as the Heck and Suzuki coupling) are facilitated by catalysis with palladium compounds. In addition palladium, when dispersed on conductive materials, proves to be an excellent electrocatalyst for oxidation of primary alcohols in alkaline media.^[27]

Pd is also a versatile metal for homogeneous catalysis. It is used in combination with a broad variety of ligands for highly selective chemical transformations.

A 2008 study showed that palladium is an effective catalyst for making carbon-fluoride bonds.^[28]

Palladium is found in the Lindlar catalyst, also called Lindlar's Palladium.

Electronics

The second biggest application of palladium in electronics is making the multilayer ceramic capacitor.^[29] Palladium (and palladium-silver alloys) are used as electrodes in multi-layer ceramic capacitors.^[23] Palladium (sometimes alloyed with nickel) is used in connector platings in consumer electronics.

It is also used in plating of electronic components and in soldering materials. The electronic sector consumed 1.07 million troy ounces (33.2 tonnes) of palladium in 2006, according to a Johnson Matthey report.^[30]

Technology

Hydrogen easily diffuses through heated palladium; thus, it provides a means of purifying the gas.^[11] Membrane reactors with Pd membranes are therefore used for the production of high purity hydrogen.

It is a part of the palladium-hydrogen electrode in electrochemical studies. Palladium(II) chloride can absorb large amounts of carbon monoxide gas, and is used in carbon monoxide detectors.

Hydrogen storage

Palladium hydride is metallic palladium that contains a substantial quantity of hydrogen within its crystal lattice. At room temperature and atmospheric pressure, palladium can absorb up to 900 times its own volume of hydrogen in a reversible process. This property has been investigated because hydrogen storage is of such interest and a better understanding of what happens at the molecular level could give clues to designing improved metal hydrides. A palladium based store, however, would be prohibitively expensive due to the cost of the metal.^[31]

Jewelry

Palladium itself has been used as a precious metal in jewelry since 1939, as an alternative to platinum or white gold. This is due to its naturally white properties, giving it no need for rhodium plating. It is slightly whiter, much lighter and about 12% harder than platinum. Similar to gold, palladium can be beaten into a thin leaf form as thin as 100 nm (1/250,000 in).^[11] Like platinum, it will develop a hazy patina over time. Unlike platinum, however, palladium may discolor at high soldering temperatures, become brittle with repeated heating and cooling, and react with strong acids.^[32]

Palladium is one of the three most popular metals used to make white gold alloys.^[23] (Nickel and silver can also be used.) Palladium-gold is a more expensive alloy than nickel-gold, but seldom causes allergic reactions (though certain cross-allergies with nickel may occur).^[33]

When platinum was declared a strategic government resource during World War II, many jewelry bands were made out of palladium.^[34] As recently as September 2001,^[35] palladium was more expensive than platinum and rarely used in jewelry also due to the technical obstacle of casting. However the casting problem has been resolved, and its use in jewelry has increased because of a large spike in the price of platinum and a drop in the price of palladium.^[36]

Prior to 2004, the principal use of palladium in jewelry was as an alloy in the manufacture of white gold jewelry, but, beginning early in 2004 when gold and platinum prices began to rise steeply, Chinese jewelers began fabricating significant volumes of palladium jewelry. Johnson Matthey estimated that in 2004, with the introduction of palladium jewelry in China, demand for palladium for jewelry fabrication was 920,000 ounces, or approximately 14% of the total palladium demand for 2004 - an increase of almost 700,000 ounces from the previous year. This growth continued during 2005, with estimated worldwide jewelry demand for palladium of about 1.4 million ounces, or almost 21% of net palladium supply, again with most of the demand centered in China. The popularity of palladium jewelry is expected to grow in 2008 as the world's biggest producers embark on a joint marketing effort to promote palladium jewelry worldwide ^[37]

Photography

With the platinotype printing process photographers make fine-art black-and-white prints using platinum or palladium salts. Often used with platinum, palladium provides an alternative to silver.^[38]

Art

Palladium leaf is one of several alternatives to silver leaf used in manuscript illumination. The use of silver leaf is problematic because it tarnishes quickly, dulling the appearance and requiring constant cleaning. Palladium is a suitable substitute due to its resistance to tarnishing. Aluminium leaf is another inexpensive alternative, but aluminium is much more difficult to work than gold or silver and results in less than optimal results when employing traditional metal leafing techniques, so palladium leaf is considered the best substitute despite its considerable cost. Platinum leaf may be used to the same effect as palladium leaf with similar working properties, but it is not as commercially available on demand in leaf form.^[39]^[40]

Safety

Finely divided palladium metal can be pyrophoric. The bulk material is quite inert.

References

^ "Standard Atomic Weights: Palladium". CIAAW. 1979.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ ^a ^b ^c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^ Palladium(V) has been identified in complexes with organosilicon compounds containing pentacoordinate palladium; see Shimada, Shigeru; Li, Yong-Hua; Choe, Yoong-Kee; Tanaka, Masato; Bao, Ming; Uchimaru, Tadafumi (2007). "Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms". Proceedings of the National Academy of Sciences. 104 (19): 7758–7763. doi:10.1073/pnas.0700450104. PMC 1876520. PMID 17470819.
^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^ "Palladium". International Platinum Group Metals Association.
^ W. P. Griffith (2003). "Rhodium and Palladium - Events Surrounding Its Discovery". Platinum Metals Review. 47 (4): 175–183.
^ Wollaston, W. H. (1804). "On a New Metal, Found in Crude Platina". Philosophical Transactions of the Royal Society of London. 94: 419–430. doi:10.1098/rstl.1804.0019.
^ ^a ^b ^c ^d ^e C. R. Hammond (2004). The Elements, in Handbook of Chemistry and Physics 81th edition. CRC press. ISBN 0849304857.
^ Garrett, Christine E. (2004). "The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd-Catalyzed Reactions". Advanced Synthesis & Catalysis. 346 (8): 889–900. doi:10.1002/adsc.200404071. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
^ Alan Williamson. "Russian PGM Stocks" (PDF). The LBMA Precious Metals Conference 2003. The London Bullion Market Association.
^ "Historical Palladium Charts and Data". Kitco. Retrieved 2007-08-09.
^ "Ford fears first loss in a decade". BBC News. 2002-01-16. Retrieved 2008-09-19.
^ "Platinum-Group Metals" (PDF). Mineral Commodity Summaries. United States Geological Survey. 2007. {{cite web}}: Unknown parameter |month= ignored (help)
^ J. Kielhorn; C. Melber; D. Keller; I. Mangelsdorf (2002). "Palladium – A review of exposure and effects to human health". International Journal of Hygiene and Environmental Health. 205 (6): 417. doi:10.1078/1438-4639-00180. PMID 12455264. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ Gray, Theodore. "46 Palladium". Element Displays. Retrieved 2007-10-14.
^ "Atomic Weights and Isotopic Compositions for Palladium (NIST)". Retrieved 2009-11-12.
^ W. R. Kelly; G. J. Wasserburg (1978). "Evidence for the existence of ¹⁰⁷Pd in the early solar system". Geophysical Research Letters. 5: 1079–1082. doi:10.1098/rsta.2001.0893. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ J. H. Chen; G. J. Wasserburg (1990). "The isotopic composition of Ag in meteorites and the presence of ¹⁰⁷Pd in protoplanets". Geochimica et Cosmochimica Acta. 54 (6): 1729–1743. doi:10.1016/0016-7037(90)90404-9. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ Gordon K. Anderson; Minren Lin; Sen, Ayusman; Gretz, Efi (1990). "Bis(Benzonitrile)Dichloro Complexes of Palladium and Platinum". Inorganic Syntheses. 28: 60–63. doi:10.1002/9780470132593.ch13. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ ^a ^b ^c ^d "Palladium". United Nations Conference on Trade and Development. Retrieved 2007-02-05.
^ Roy Rushforth (2004). "Palladium in Restorative Dentistry: Superior Physical Properties make Palladium an Ideal Dental Metal". Platinum Metals Review. 48 (1).
^ Hesse, Rayner W. (2007). "palladium". Jewelry-making through history: an encyclopedia. Greenwood Publishing Group. p. 146.
^ Toff, Nancy (1996). The flute book: a complete guide for students and performers. Oxford University Press. p. 20. ISBN 9780195105025.
^ Jiro Tsuji (2004). Palladium reagents and catalysts: new perspectives for the 21st century. John Wiley and Sons. p. 90. ISBN 0470850329.
^ Chemical & Engineering News Vol. 86 No. 35, 1 Sept. 2008, "Palladium's Hidden Talent", p. 53
^ Dennis Zogbi (February 3, 2003). "Shifting Supply and Demand for Palladium in MLCCs". TTI, Inc.
^ David Jollie (2007). "Platinum 2007" (PDF). Johnson Matthey.
^ W. Grochala; P. P. Edwards (2004). "Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen". Chem. Rev. 104 (3): 1283–1316. doi:10.1021/cr030691s. PMID 15008624. {{cite journal}}: Unknown parameter |author-separator= ignored (help)
^ Emil Raymond Riegel, James A. Kent (2007). Kent and Riegel's Handbook of Industrial Chemistry and Biotechnology. Springer. p. 1037. ISBN 0387278427.
^ "Cross-reactivity between nickel and palladium demonstrated by systemic administration of nickel". PubMed. Retrieved 2009-06-06.
^ "What Is Palladium?". Jewelry.com. November 3, 2008.
^ "Daily Metal Prices: September 2001". Johnson Matthey.
^ Holmes, E. (February 13, 2007). "Palladium, Platinum's Cheaper Sister, Makes a Bid for Love". Wall Street Journal (Eastern edition). pp. B.1.
^ "Stillwater Mining Up on Jewelry Venture". Yahoo Finance.
^ Mike Ware (2005). "Book Review of : Photography in Platinum and Palladium". Platinum Metals Review. 49 (4): 190–195. doi:10.1595/147106705X70291.
^ Margaret Morgan (2007). The Bible of Illuminated Letters. Barron's Educational Series. p. 50. ISBN 978-0764158209.
^ "Palladium Leaf". Theodore Gray.

External links

[1] "Standard Atomic Weights: Palladium". CIAAW. 1979.

[CIAAW2021-2] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[Arblaster_2018-3] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[4] Palladium(V) has been identified in complexes with organosilicon compounds containing pentacoordinate palladium; see Shimada, Shigeru; Li, Yong-Hua; Choe, Yoong-Kee; Tanaka, Masato; Bao, Ming; Uchimaru, Tadafumi (2007). "Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms". Proceedings of the National Academy of Sciences. 104 (19): 7758–7763. doi:10.1073/pnas.0700450104. PMC 1876520. PMID 17470819.

[5] Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

[6] Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.

[NUBASE2020-7] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[8] "Palladium". International Platinum Group Metals Association.

[9] W. P. Griffith (2003). "Rhodium and Palladium - Events Surrounding Its Discovery". Platinum Metals Review. 47 (4): 175–183.

[10] Wollaston, W. H. (1804). "On a New Metal, Found in Crude Platina". Philosophical Transactions of the Royal Society of London. 94: 419–430. doi:10.1098/rstl.1804.0019.

[CRC-11] C. R. Hammond (2004). The Elements, in Handbook of Chemistry and Physics 81th edition. CRC press. ISBN 0849304857.

[12] Garrett, Christine E. (2004). "The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd-Catalyzed Reactions". Advanced Synthesis & Catalysis. 346 (8): 889–900. doi:10.1002/adsc.200404071. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

[13] Alan Williamson. "Russian PGM Stocks" (PDF). The LBMA Precious Metals Conference 2003. The London Bullion Market Association.

[14] "Historical Palladium Charts and Data". Kitco. Retrieved 2007-08-09.

[15] "Ford fears first loss in a decade". BBC News. 2002-01-16. Retrieved 2008-09-19.

[16] "Platinum-Group Metals" (PDF). Mineral Commodity Summaries. United States Geological Survey. 2007. {{cite web}}: Unknown parameter |month= ignored (help)

[Kielhorn-17] J. Kielhorn; C. Melber; D. Keller; I. Mangelsdorf (2002). "Palladium – A review of exposure and effects to human health". International Journal of Hygiene and Environmental Health. 205 (6): 417. doi:10.1078/1438-4639-00180. PMID 12455264. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[Gray-18] Gray, Theodore. "46 Palladium". Element Displays. Retrieved 2007-10-14.

[19] "Atomic Weights and Isotopic Compositions for Palladium (NIST)". Retrieved 2009-11-12.

[20] W. R. Kelly; G. J. Wasserburg (1978). "Evidence for the existence of ¹⁰⁷Pd in the early solar system". Geophysical Research Letters. 5: 1079–1082. doi:10.1098/rsta.2001.0893. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[21] J. H. Chen; G. J. Wasserburg (1990). "The isotopic composition of Ag in meteorites and the presence of ¹⁰⁷Pd in protoplanets". Geochimica et Cosmochimica Acta. 54 (6): 1729–1743. doi:10.1016/0016-7037(90)90404-9. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[22] Gordon K. Anderson; Minren Lin; Sen, Ayusman; Gretz, Efi (1990). "Bis(Benzonitrile)Dichloro Complexes of Palladium and Platinum". Inorganic Syntheses. 28: 60–63. doi:10.1002/9780470132593.ch13. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[unctad-23] "Palladium". United Nations Conference on Trade and Development. Retrieved 2007-02-05.

[24] Roy Rushforth (2004). "Palladium in Restorative Dentistry: Superior Physical Properties make Palladium an Ideal Dental Metal". Platinum Metals Review. 48 (1).

[25] Hesse, Rayner W. (2007). "palladium". Jewelry-making through history: an encyclopedia. Greenwood Publishing Group. p. 146.

[26] Toff, Nancy (1996). The flute book: a complete guide for students and performers. Oxford University Press. p. 20. ISBN 9780195105025.

[27] Jiro Tsuji (2004). Palladium reagents and catalysts: new perspectives for the 21st century. John Wiley and Sons. p. 90. ISBN 0470850329.

[28] Chemical & Engineering News Vol. 86 No. 35, 1 Sept. 2008, "Palladium's Hidden Talent", p. 53

[29] Dennis Zogbi (February 3, 2003). "Shifting Supply and Demand for Palladium in MLCCs". TTI, Inc.

[matthey-30] David Jollie (2007). "Platinum 2007" (PDF). Johnson Matthey.

[grochala-31] W. Grochala; P. P. Edwards (2004). "Thermal Decomposition of the Non-Interstitial Hydrides for the Storage and Production of Hydrogen". Chem. Rev. 104 (3): 1283–1316. doi:10.1021/cr030691s. PMID 15008624. {{cite journal}}: Unknown parameter |author-separator= ignored (help)

[32] Emil Raymond Riegel, James A. Kent (2007). Kent and Riegel's Handbook of Industrial Chemistry and Biotechnology. Springer. p. 1037. ISBN 0387278427.

[33] "Cross-reactivity between nickel and palladium demonstrated by systemic administration of nickel". PubMed. Retrieved 2009-06-06.

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@@ Line 104: / Line 104: @@
 ==Applications==
-Palladium is used in jewelry, in [[dentistry]],<ref name=unctad/><ref>{{cite journal|journal = Platinum Metals Review|title = Palladium in Restorative Dentistry: Superior Physical Properties make Palladium an Ideal Dental Metal|author = Roy Rushforth|volume = 48|issue = 1|year = 2004|url = http://www.platinummetalsreview.com/dynamic/article/view/48-1-030-031}}</ref> [[watch]] making, in blood sugar test strips, in aircraft [[spark plug]]s and in the production of [[surgical instrument]]s and [[electrical contact]]s.<ref>{{ cite book|title = Jewelry-making through history: an encyclopedia|first = Rayner W.|last = Hesse|publisher = Greenwood Publishing Group|year = 2007|pages = 146|url = http://books.google.com/books?id=DIWEi5Hg93gC&pg=PA146|chapter = palladium}}</ref> Palladium is also used to make professional [[transverse flute]]s.<ref>{{cite book|title = The flute book: a complete guide for students and performers
+The largest use of palladium today is in catalytic converters.<ref name=unctad/> Palladium is also used in jewelry, in [[dentistry]],<ref name=unctad/><ref>{{cite journal|journal = Platinum Metals Review|title = Palladium in Restorative Dentistry: Superior Physical Properties make Palladium an Ideal Dental Metal|author = Roy Rushforth|volume = 48|issue = 1|year = 2004|url = http://www.platinummetalsreview.com/dynamic/article/view/48-1-030-031}}</ref> [[watch]] making, in blood sugar test strips, in aircraft [[spark plug]]s and in the production of [[surgical instrument]]s and [[electrical contact]]s.<ref>{{ cite book|title = Jewelry-making through history: an encyclopedia|first = Rayner W.|last = Hesse|publisher = Greenwood Publishing Group|year = 2007|pages = 146|url = http://books.google.com/books?id=DIWEi5Hg93gC&pg=PA146|chapter = palladium}}</ref> Palladium is also used to make professional [[transverse flute]]s.<ref>{{cite book|title = The flute book: a complete guide for students and performers
 | first = Nancy|last = Toff|publisher = Oxford University Press|year = 1996|pages =20|isbn = 9780195105025|url = http://books.google.com/books?id=pCSanDD4CtsC&pg=PA20}}</ref> As a commodity, palladium [[bullion]] has [[ISO currency code]]s of XPD and 964. Palladium is one of only four metals to have such codes, the others being [[gold]], [[silver]] and [[platinum]].
+===Catalysis===
+When it is finely divided, such as in [[palladium on carbon]], palladium forms a versatile [[catalyst]] and speeds up [[hydrogenation]] and [[dehydrogenation]] reactions, as well as in [[cracking (chemistry)|petroleum cracking]]. A large number of [[carbon-carbon bond]] forming reactions in [[organic chemistry]] (such as the Heck and [[Suzuki coupling]]) are facilitated by catalysis with palladium compounds. In addition palladium, when dispersed on conductive materials, proves to be an excellent electrocatalyst for oxidation of primary alcohols in alkaline media.<ref>{{cite book|page=90|url=http://books.google.com/books?id=RDT0OUdlj0MC&pg=PA90| title=Palladium reagents and catalysts: new perspectives for the 21st century| author=Jiro Tsuji
+|publisher= John Wiley and Sons|year = 2004| isbn =0470850329}}</ref>
+Pd is also a versatile metal for [[homogeneous catalysis]]. It is used in combination with a broad variety of [[ligands]] for highly selective chemical transformations.
+A 2008 study showed that palladium is an effective catalyst for making carbon-fluoride bonds.<ref>[[Chemical & Engineering News]] Vol. 86 No. 35, 1 Sept. 2008, "Palladium's Hidden Talent", p. 53</ref>
+Palladium is found in the [[Lindlar catalyst]], also called Lindlar's Palladium.
 ===Electronics===
 The second biggest application of palladium in electronics is making the [[multilayer ceramic capacitor]].<ref>{{cite web|url = http://www.ttiinc.com/object/ME_Zogbi_20030203.html|title = Shifting Supply and Demand for Palladium in MLCCs|author = Dennis Zogbi|date = February 3, 2003|publisher = TTI, Inc.}}</ref> Palladium (and palladium-silver alloys) are used as electrodes in multi-layer ceramic [[Capacitor (component)|capacitors]].<ref name=unctad/> Palladium (sometimes alloyed with nickel) is used in connector platings in consumer electronics.
@@ Line 116: / Line 125: @@
 It is a part of the [[palladium-hydrogen electrode]] in electrochemical studies. [[Palladium(II) chloride]] can absorb large amounts of carbon monoxide gas, and is used in [[carbon monoxide detectors]].
-===Catalysis===
-When it is finely divided, such as in [[palladium on carbon]], palladium forms a versatile [[catalyst]] and speeds up [[hydrogenation]] and [[dehydrogenation]] reactions, as well as in [[cracking (chemistry)|petroleum cracking]]. A large number of [[carbon-carbon bond]] forming reactions in [[organic chemistry]] (such as the Heck and [[Suzuki coupling]]) are facilitated by catalysis with palladium compounds. The largest use of palladium today is in catalytic converters.<ref name=unctad/> In addition palladium, when dispersed on conductive materials, proves to be an excellent electrocatalyst for oxidation of primary alcohols in alkaline media.<ref>{{cite book|page=90|url=http://books.google.com/books?id=RDT0OUdlj0MC&pg=PA90| title=Palladium reagents and catalysts: new perspectives for the 21st century| author=Jiro Tsuji
-|publisher= John Wiley and Sons|year = 2004| isbn =0470850329}}</ref>
-Pd is also a versatile metal for [[homogeneous catalysis]]. It is used in combination with a broad variety of [[ligands]] for highly selective chemical transformations.
-A 2008 study showed that palladium is an effective catalyst for making carbon-fluoride bonds.<ref>[[Chemical & Engineering News]] Vol. 86 No. 35, 1 Sept. 2008, "Palladium's Hidden Talent", p. 53</ref>
-Palladium is found in the [[Lindlar catalyst]], also called Lindlar's Palladium.
 ===Hydrogen storage===