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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: 1554.9°C
Boiling point: 2963°C
Thermal conductivity/Wm-1K-1: 71.8 (27°C)
Density/kgm-3: 12020 (20°C), 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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