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Element Fact
The liquid helium-4 possesses the most unusual physical properties that defy common sense. Below 2.2 K it becomes a superfluid that can flow, against gravity, up the wall of a container.

Palladium, Pd

palladium sample

Atomic number: 46
Atomic mass: 106.42(1)
Natural abundance: 0.015 ppm
102Pd (101.905608) - 1.02%
104Pd (103.904035) - 11.14%
105Pd (104.905084) - 22.33%
106Pd (105.903483) - 27.33%
108Pd (107.903894) - 26.46%
110Pd (109.905150) - 11.72%

History and Production

It was names after the asteroid Pallas, which in Greek means goddessof wisdom. The element was discovered by W.H. Wollaston in 1803 in the course of his study of platinum. It is obtained from anode slimes in the electrolytic refinement of other metals such as copper and nickel. It is dissolved out when aqua regia is added. It is used to purify hydrogen gas and as a catalyst for hydrogenation and dehydrogenation processes. It is also used in dentistry, surgical intruments and electrical contacts. In jewellery, it is alloyed with gold to make white gold.

Physical Data

It is silvery-white and lustrous that does not tarnish in air. It is malleable and ductile. At room temeprature it can adsorb hydrogen up to 900 times of its own volume. The gas is released when metal is heated. Palladium is quite rare, about 0.015 ppm in abundance. It often exists as native with other platinum metals and also with copper and nickel sulfide ores in Sudbury, Ontario.

Interatomic distance: 275.2 pm
Melting point: 1554.9C
Boiling point: 2963C
Thermal conductivity/Wm-1K-1: 71.8 (27C)
Density/kgm-3: 12020 (20C), 10379 (m.p.)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 378.2 kJ/mol
Gibbs free energy of formation: 339.7 kJ/mol
Entropy: 167.1 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Kr] 4d10
Term symbol: 1S0
Electron affinity: 54.2248 kJ/mol   Electronegativity (Pauline): 2.20
Ionization energy (first, second, third): 804.389, 1874.71, 3177.26 kJ/mol

Chemical properties

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