Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM).
Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. It has a coefficient of expansion almost equal to that of soda-lime-silica glass, and is therefore used to make sealed electrodes in glass systems.
The metal does not oxidise in air. It is insoluble in hydrochloric and nitric acid, but dissolves when they are mixed as aqua regia, forming chloroplatinic acid (H2PtCl6), an important compound. It is corroded by halogens, cyanides, sulphur and alkalis. Hydrogen and oxygen gas mixtures explode in the presence of platinum wire.
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of platinum where known.
Isotope abundances of platinum with the most intense signal set to 100%.
- Platinum isotopes are used in the following fields. Pt-196 is used in experiments to test nuclear models. Both Pt-194 and Pt-196 have been used in research into dipole strength and models. Pt-195 is used for the production of the radioisotope Pt-195m which is used for cancer diagnosis and therapy. Pt-198 is used for the production of the radioisotope for Au-199 which is used in cancer therapy. Pt-194 is also used for the production of the medical radioisotopes Hg-195m.
Isolation: it would not normally be necessary to make a sample of platinum in the laboratory as the metal is available commercially. The industrial extraction of platinum is complex as the metal occurs in ores mixed with other metals such as palladium and gold. Sometimes extraction of the precious metals such as platinum and palladium is the main focus of a partiular industrial operation while in other cases it is a byproduct. The extraction is complex and only worthwhile since platinum is the basis of important catalysts in industry.
Preliminary treatment of the ore or base metal byproduct with aqua regia (a mixture of hydrochloric acid, HCl, and nitric acid, HNO3) gives a solution containing complexes of gold and palladium as well as H2PtCl6. The gold is removed from this solution as a precipitate by treatment with iron chloride (FeCl2). The platinum is precipitated out as impure (NH4)2PtCl6 on treatment with NH4Cl, leaving H2PdCl4 in solution. The (NH4)2PtCl6 is burned to leave an impure platinum sponge. This can be purified by redissolving in aqua regia, removal of rhodium and iridium impurities by treatment of the solution with sdoium bromate, and precipitation of pure (NH4)2PtCl6 by treatment with ammonium hydroxide, NH4OH. This yields platinum metal by burning.
Density of solid: 21090 kg m-3
Molar volume: 9.09 cm3
Thermal conductivity: 72 W m‑1 K‑1
Melting point: 2041.4 [1768.3 °C (3214.9 °F)] K
Boiling point: 4098 [3825 °C (6917 °F)] K
Enthalpy of fusion: 20.5 kJ mol-1
Atomic radius (empirical): 135 pm
Molecular single bond covalent radius: 123 (coordination number 3) ppm
van der Waals radius: 232 ppm
Pauling electronegativity: 2.28 (Pauling units)
Allred Rochow electronegativity: 1.44 (Pauling units)
Mulliken-Jaffe electronegativity: (no data)
First ionisation energy: 864.40 kJ mol‑1
Second ionisation energy: 1791 kJ mol‑1
Third ionisation energy: 2800 kJ mol‑1
Universe: 5 ppb by weight
Crustal rocks: 37 ppb by weight
Human: (no data) ppb by weight
