Platinum
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Platinum, Pt | ||||
| Appearance | Silvery white metal | ||||
| Platinum in the periodic table | |||||
| |||||
| Atomic number | 78 | ||||
| Standard atomic weight (Ar) | 195.084(9) | ||||
| Group, block | , d-block | ||||
| Period | period 6 | ||||
| Electron configuration | [Xe] 4f14 5d9 6s1 | ||||
per shell | 2, 8, 18, 32, 17, 1 | ||||
| Physical properties | |||||
| Silvery-white | |||||
| Phase | Solid | ||||
| Melting point | 2041.4 K (1768.3 °C, 3214.9 °F) | ||||
| Boiling point | 4098 K (3825 °C, 6917 °F) | ||||
| Density near r.t. | 21.45 g/cm3 | ||||
| when liquid, at | 19.77 g/cm3 | ||||
| Heat of fusion | 22.17 kJ/mol | ||||
| Heat of | 510 kJ/mol | ||||
| Molar heat capacity | 25.86 J/(mol·K) | ||||
| pressure | |||||
| Atomic properties | |||||
| Oxidation states | 6, 5, 4, 3, 2, 1, −1, −2, −3 (a mildly basic oxide) | ||||
| Electronegativity | Pauling scale: 2.28 | ||||
| energies |
1st: 870 kJ/mol 2nd: 1791 kJ/mol | ||||
| Atomic radius | empirical: 139 pm | ||||
| Covalent radius | 136±5 pm | ||||
| Van der Waals radius | 175 pm | ||||
| Miscellanea | |||||
| Crystal structure | Face-centered cubic (fcc) | ||||
| Speed of sound thin rod | 2800 m/s (at ) | ||||
| Thermal expansion | 8.8 µm/(m·K) (at 25 °C) | ||||
| Thermal conductivity | 71.6 W/(m·K) | ||||
| Electrical resistivity | 1.05·10-7 Ω·m (at 20 °C) | ||||
| Magnetic ordering | Paramagnetic | ||||
| Tensile strength | 125–240 MPa | ||||
| Young's modulus | 168 GPa | ||||
| Shear modulus | 61 GPa | ||||
| Bulk modulus | 230 GPa | ||||
| Poisson ratio | 0.38 | ||||
| Mohs hardness | 3.5 | ||||
| Vickers hardness | 400–550 MPa | ||||
| Brinell hardness | 300–500 MPa | ||||
| CAS Registry Number | 7440-06-4 | ||||
| History | |||||
| Discovery | Antonio de Ulloa (1748) | ||||
Platinum is a chemical element with the chemical symbol Pt and the atomic number 78. It is a valuable and useful transition metal, part of the so called "platinum group metals".
Contents
Properties
Chemical
Platinum is extremely resistant to organic and mineral acids. It will, however, dissolve extremely slowly in hot aqua regia, to give chloroplatinic acid.
- Pt + 4 HNO3 + 6 HCl → H2PtCl6 + 4 NO2 + 4 H2O
It will also be attacked by molten alkali and cyanides.
Physical
Platinum is a lustrous, ductile, and malleable, silver-white metal. It is more ductile than gold, but less malleable.
Availability
Although it can be bought from precious metal stores, platinum is also found in certain electronics and car exhaust catalysts. Electrodes are sometimes coated with platinum. Platinum can be obtained along with silver in small amounts from capacitors obtained through electronic recycling.
Platinum bullion can be bought, which has the advantage of having purity expressed accurately.
In Australia, platinum is classified as Category II precursor chemical and purchasing it requires and EUD.[1]
Isolation
Platinum can be extracted by dissolving it in aqua regia. The resulting chloroplatinic acid is converted to ammonium chloroplatinate by the addition of ammonium chloride, that can be reduced to platinum metal by heating it, usually in a hydrogen atmosphere. This results in a platinum sponge.
Projects
- Make chloroplatinic acid
- Make platinum electrodes
- Electrolysis
- Make chlorates and perchlorates
Handling
Safety
Being a noble metal, it is non-toxic, though some of its compounds should be handled with care, as they're toxic.
Storage
No special storage is required for storing platinum, though platinum electrodes should be kept away from sulfur oxides which can "poison" it.
Disposal
It's best to recycle platinum, considering it's a rare and expensive metal.
