Platinum

78

Pt

195.084(9)
  • Name: Platinum
  • Symbol: Pt
  • Atomic number: 78
  • Atomic weight: 195.084(9)
  • CAS Registry ID: 7440-06-4
  • Group name: Precious metal
  • Period number: 6
  • Block: d-block
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Description

Platinum is a lustrous, grey white, transition metal in its natural solid state. It is resistant to corrosion and has strong catalytic properties. Platinum has an atomic weight of 195.084, a melting point of 3214.9 °F, and a boiling point of 6917 °F. Some common uses of platinum include: as a catalyst component in catalytic converters and fuel cells, in the form of electrodes for electrolytic reactions, as a component in precious jewelry, as a catalyst in glow plugs, and as a component for certain types of photography.

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Isolation

Platinum does occur in its free state in nature, but it is very rare. Isolation processes can be used to isolate platinum from such minerals as iridium and platiniridium.

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As a rare and precious metal, platinum is only extracted and isolated on a commercial basis; small scale laboratory isolation of platinum is too expensive and energetically inefficient. The isolation process of platinum begins with treating the ore it occurs in with a mixture of hydrochloric acid and nitric acid. This results in a solution which contains any gold and palladium complexes in the mineral, in addition to a hydrogen platinum chorine compound. Iron chloride is added to the solution to precipitate out any gold; impure platinum is removed by treating the solution with ammonium chloride in the form of a precipitate. The impure precipitate compound containing platinum is then burned resulting in a platinum sponge which contains impurities. Further platinum isolation is carried out by treating the sponge with a mixture of hydrochloric acid and nitric acid; sodium bromated removes additional impurities, and the resulting product is treated with ammonium hydroxide and then burned which yields pure platinum metal isolation.
General
Name Platinum
Symbol Pt
Number 78
Chemical series transition metals
Group 10
Period 6
Block d
Appearance grayish white
Standard atomic weight 195.084(9)  g·mol−1
Electron configuration [Xe] 4f14 5d9 6s1
Electrons per shell 2, 8, 18, 32, 17, 1
Atomic properties
Crystal structure cubic face centered
Oxidation states 1, 2, 3, 4, 5, 6 (mildly basic oxide)
Electronegativity 2.28 (scale Pauling)
Ionization energies 1st: 870 kJ/mol
(more) 2nd: 1791 kJ/mol
(more)
Atomic radius 135 pm
Atomic radius (calc.) 177 pm
Covalent radius 128 pm
Van der Waals radius 175 pm
Physical properties
Phase solid
Density (near r.t.) 21.45  g·cm−3
Liquid density at m.p. 19.77  g·cm−3
Melting point 2041.4 K (1768.3 °C, 3214.9 °F)
Boiling point 4098 K (3825 °C, 6917 °F)
Critical point
Heat of fusion 22.17  kJ·mol−1
Heat of vaporization 469  kJ·mol−1
Heat capacity (25 °C) 25.86  J·mol−1·K−1
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 105 n Ω·m
Thermal conductivity (300 K) 71.6  W·m−1·K−1
Thermal expansion (25 °C) 8.8  µm·m−1·K−1
Speed of sound (thin rod) (r.t.) 2800  m·s−1
Young's modulus 168 GPa
Shear modulus 61 GPa
Bulk modulus 230 GPa
Poisson ratio 0.38
Mohs hardness 4 - 4.5
Vickers hardness 549 MPa
Brinell hardness 392 MPa
CAS registry number 7440-06-4

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