Physical Properties
Platinum is a grayish-white metal that will not oxidize in the air, but can be corroded with alkalis, sulfur, cyanides or halogens. Its molar volume is 9.09 centimeters cubed and its velocity of sound is 2,680 m/s. Platinum's hardness is 4 to 4.5 -- unusually high for a metal -- but it is still malleable. It has a bright metallic luster. It is typically found with copper, nickel, iron and gold and sometimes with rare earth elements; this can lower its specific gravity to as low as 14. The specific gravity of pure platinum is normally 21.4.
Temperature and Ethalpies
Platinum melts at 3,214.9 degrees Fahrenheit and boils at 6,917 degrees Fahrenheit, giving it a liquid range of 3,242.1 degrees Fahrenheit. Platinum's crystal structure is cubic close-packed. Its enthalpy of fusion is 20 kJ/mol, its enthalpy of vaporization is 490 kJ/mol and its enthalpy of atomization is 565 kJ/mol. There is no data available on platinum's critical temperature or its superconduction temperature.
Atomic and Nuclear Properties
The atomic weight of platinum is 195.084 and there are 78 neutrons in a platinum atom. Platinum's empirical atomic radius is 135 pm, while its calculated atomic radius is 177 pm. At 20 degrees Celsius, it has a density of 21.4 grams/cc. Its van der Waals radius is 0.138 nm and it Pauling electronegativity is 2.2.
Isotopes
There are six naturally occurring platinum isotopes, some of which have several experimental and medical uses. Platinum-196 is used in nuclear model testing and has been used along with platinum-194 to research dipole strength. The radioisotope platinum-195m, produced from platinum-195, is used to diagnose cancer and provide therapy. Platinum-198 is also used to produce a radioisotope (gold-199) for cancer therapy. The medical radioisotope mercury-195m is made using platinum-194. Platinum 190 and 192 are also naturally occurring.