Palladium

Palladium - Pd

CAS: 7440-05-3
Description: Soft, white metal
Classification: Transition Metal
Date of Discovery: 1803
Discoverer: William Wollaston
Name Origin: Greek goddess of wisdom, Pallas; asteroid Pallas

Atomic Number: 46
Number of Neutrons: 60
Atomic Mass: 106.42(1) amu
Melting Point: 1554.9 °C
Boiling Point: 2963 °C
Density (293 K): 12.02 g/cm³
Atomic volume: 8.9 cm³/mol
Electrical resistivity: 0.718 10^-6/cm

Thermal conductivity: 0.907 W/cmK
Enthalpy of atomization: 393.3 kJ/mol (est.)
Enthalpy of vaporization: 357.0 kJ/mol
Enthalpy of fusion: 17.60 kJ/mol
Specific heat capacity: 0.24 J/gK

Energy levels: 2-8-18-18
Electron configuration: [Kr]4d¹⁰
Crystal Structure: Cubic face centered
Atomic radius: 1.79 Å
Covalent radius: 1.28 Å
Oxidation States: +2, +3, +4
Electronegativity, Pauling: 2.20
Electron affinity: 0.562 eV
First ionization energy: 8.34 eV
2nd ionization energy: 19.63 eV
3rd ionization energy: 32.93 eV
Polarizability: 4.8 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
⁹²Pd
⁹³Pd
⁹⁴Pd	93.9288	9 s	EC, ⁺
^95mPd	94.92684	13.4 s	EC, ⁺	21/2+
⁹⁵Pd
⁹⁶Pd	95.9182	2.03 m	EC, ⁺
⁹⁷Pd	99.9165	3.1 m	⁺, EC	5/2+
⁹⁸Pd	97.91273	17.7 m	⁺; EC	0+
⁹⁹Pd	98.91181	21.4 m	⁺; EC	5/2+
¹⁰⁰Pd	99.90851	3.7 d	EC	0+
¹⁰¹Pd	100.90829	8.4 h	⁺; EC	5/2+
¹⁰²Pd	1.02(1)	101.905607	Stable	0+
¹⁰³Pd	102.906087	16.99 d	EC	5/2+
¹⁰⁴Pd	11.14(8)	103.904034	Stable	0+
¹⁰⁵Pd	22.33(8)	104.905083	Stable	5/2+
¹⁰⁶Pd	27.33(3)	105.903484	Stable	0+
^107mPd	20.9 s	IT	11/2-
¹⁰⁷Pd	106.90513	6.5 x 10⁶ y	^-	5/2+
¹⁰⁸Pd	26.46(9)	107.903895	Stable	0+
^109mPd	4.75 m	IT	11/2-
¹⁰⁹Pd	108.905954	13.5 h	^-	5/2+
¹¹⁰Pd	11.72(9)	109.905153	Stable	0+
^111mPd	5.5 h	IT; ^-	11/2-
¹¹¹Pd	110.90764	23.4 m	^-	5/2+
¹¹²Pd	111.90731	21.04 h	^-	0+
^113mPd	1.48 m	^-	5/2+
¹¹³Pd	112.9105	1.64 m	^-
¹¹⁴Pd	113.91037	2.48	^-	0+
¹¹⁵Pd	114.9137	47 s	^-
¹¹⁶Pd	115.9142	12.7 s	^-
¹¹⁷Pd	116.9178	4.4 s	^-
¹¹⁸Pd	117.9189	2.4 s	^-
¹¹⁹Pd	118.9227	0.9 s	^-
¹²⁰Pd	119.9240	0.9 s	^-
Discovered in 1803 by Wollaston. Palladium is found along with platinum and other metals of the platinum group in placer deposits of Russia, South and North America, Ethiopia, and Australia. Natural palladium contains six stable isotopes. Twenty-five other isotopes are recognized, all of which are radioactive. It is also found associated with the nickel-copper deposits of South Africa and Ontario. Its separation from the platinum metals depends upon the type of ore in which it is found. It is a steel-white metal, does not tarnish in air, and is the least dense and lowest melting of the platinum group of metals. When annealed, it is soft and ductile; cold working greatly increases its strength and hardness. Palladium is attacked by nitric and sulfuric acid. At room temperatures the metal has the unusual property of absorbing up to 900 times its own volume of hydrogen, possibly forming Pd₂H. It is not yet clear if this a true compound. Hydrogen readily diffuses through heated palladium and this provides a means of purifying the gas. Finely divided palladium is a good catalyst and is used for hydrogenation and dehydrogenation reactions. It is alloyed and used in jewelry trades. White gold is an alloy of gold decolorized by the addition of palladium. Like gold, palladium can be beaten into leaf as thin as 1/250,000 in. The metal is used in dentistry, watchmaking, and in making surgical instruments and electrical contacts. LINKS: Adverse Health Effects of Palladium Combinatorial Chemistry and Palladium-catalysis Catalysis with palladium metal North American Palladium - Lac des Iles Mines Ltd. Palladium Membranes Whatever Happened to Cold Fusion? Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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