   #copyright

Platinum

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                78                iridium ← platinum → gold
                Pd
                ↑
                Pt
                ↓
                Ds

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                     Name, Symbol, Number platinum, Pt, 78
                                         Chemical series transition metals
                                             Group, Period, Block 10, 6, d
                                                  Appearance grayish white
                                             Atomic mass 195.084 (9) g/mol
                               Electron configuration [Xe] 4f^14 5d^9 6s^1
                                   Electrons per shell 2, 8, 18, 32, 17, 1
                                                       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)
                                         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

   CAPTION: Vapor pressure

                                    P/Pa   1     10   100  1 k  10 k 100 k
                                   at T/K 2330 (2550) 2815 3143 3556 4094

                                                         Atomic properties
                                     Crystal structure cubic face centered
                                                  Oxidation states 2, 3, 4
                                                      (mildly basic oxide)
                                    Electronegativity 2.28 (Pauling scale)
                                       Ionization energies 1st: 870 kJ/mol
                                                          2nd: 1791 kJ/mol
                                                      Atomic radius 135 pm
                                              Atomic radius (calc.) 177 pm
                                                    Covalent radius 128 pm
                                               Van der Waals radius 175 pm
                                                             Miscellaneous
                                            Magnetic ordering paramagnetic
                                Electrical resistivity (20 °C) 105 nΩ·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 3.5
                                                  Vickers hardness 549 MPa
                                                  Brinell hardness 392 MPa
                                             CAS registry number 7440-06-4
                                                         Selected isotopes

                 CAPTION: Main article: Isotopes of platinum

                             iso     NA    half-life  DM  DE ( MeV)   DP
                           ^190Pt   0.01% 6.5×10^11 y α   3.18      ^186Os
                           ^191Pt   syn   2.96 d      ε    ?        ^191Ir
                           ^192Pt   0.79% Pt is stable with 114 neutrons
                           ^193Pt   syn   50 y        ε    ?        ^193Ir
                           ^193 mPt syn   4.33 d      IT  0.1355 e  ^193Pt
                           ^194Pt   32.9% Pt is stable with 116 neutrons
                           ^195Pt   33.8% Pt is stable with 117 neutrons
                           ^195 mPt syn   4.02 d      IT  0.1297 e  ^195Pt
                           ^196Pt   25.3% Pt is stable with 118 neutrons
                           ^197Pt   syn   19.8913 h   β^- 0.719     ^197Au
                           ^197 mPt syn   1.59 h      IT  0.3465    ^197Pt
                           ^198Pt   7.2%  Pt is stable with 120 neutrons

                                                                References

   Platinum ( IPA: /ˈplætɪnəm/) is a chemical element in the periodic
   table that has the symbol Pt and atomic number 78. A heavy, malleable,
   ductile, precious, grey-white transition metal, platinum is resistant
   to corrosion and occurs in some nickel and copper ores along with some
   native deposits. Platinum is used in jewelry, laboratory equipment,
   electrical contacts, dentistry, and automobile emissions control
   devices.

Notable characteristics

   An assortment of native platinum nuggets
   Enlarge
   An assortment of native platinum nuggets

   When pure the metal appears greyish-white and firm. The metal is
   corrosion-resistant. The catalytic properties of the six platinum
   family metals are outstanding. For this catalytic property, platinum is
   used in catalytic converters, incorporated in automobile exhaust
   systems, as well as tips of spark plugs.

   Platinum's wear- and tarnish-resistance characteristics are well suited
   for making fine jewelry. Platinum is more precious than gold. The price
   of platinum changes along with its availability, but it normally costs
   slightly less than twice the price of gold. In the 18th century,
   platinum's rarity made King Louis XV of France declare it the only
   metal fit for a king.

   Platinum possesses remarkable resistance to chemical attack, excellent
   high-temperature characteristics, and stable electrical properties. All
   these properties have been exploited for industrial applications.
   Platinum does not oxidize in air at any temperature, but can be
   corroded by cyanides, halogens, sulfur, and caustic alkalis. This metal
   is insoluble in hydrochloric and nitric acid, but does dissolve in the
   mixture known as aqua regia (forming chloroplatinic acid). Common
   oxidation states of platinum include +2, +3, and +4.

Applications

     * As a catalyst in the catalytic converter, an optional component of
       the gasoline-fueled automobile exhaust system (see "Notable
       characteristics" in this article).
     * As a catalyst in fuel cells. Reducing the amount of platinum
       required (and thus cost) is a major focus of fuel cell research.
     * Certain platinum-containing compounds are capable of crosslinking
       (or alkylating) with DNA and are chemotherapeutic agents owing to
       this capability. For example, cisplatin, Carboplatin and
       oxaliplatin belong to this class of drugs.
     * Platinum resistance thermometers.
     * Electrodes for use in electrolysis.
     * In the Clark polarographic electrode for measuring oxygen tension.
     * A wide range of jewellery
     * As a catalyst in the curing of silicone elastomers.

History

   Naturally-occurring platinum and platinum-rich alloys have been known
   for a long time. Though the metal was used by pre-Columbian Native
   Americans, the first European reference to platinum appears in 1557 in
   the writings of the Italian humanist Julius Caesar Scaliger (1484-1558)
   as a description of a mysterious metal found in Central American mines
   between Darién (Panama) and Mexico ("up until now impossible to melt by
   any of the Spanish arts").

   Platinum was discussed by astronomer Antonio de Ulloa and Don Jorge
   Juan y Santacilia (1713-1773), both appointed by King Philip V to join
   a geographical expedition in Peru that lasted from 1735 to 1745. Among
   other things, Ulloa observed the platina del pinto, the unworkable
   metal found with gold in New Granada (Colombia). British privateers
   intercepted Ulloa's ship on the return voyage. Though he was
   well-treated in England, and even made a member of the Royal Society he
   was prevented from publishing a reference to the unknown metal until
   1748. Before that could happen Charles Wood independently isolated the
   element in 1741.

   The alchemical symbol for platinum (shown below) was made by joining
   the symbols of silver and gold.
   Alchemical symbol for platinum

   .

Occurrence

   Platinum ore
   Enlarge
   Platinum ore

   Platinum is an extremely rare metal, occurring as only 5 ppb in the
   Earth's crust.

   Platinum is often found chemically uncombined as native platinum and
   alloyed with iridium as platiniridium. The platinum arsenide,
   sperrylite (PtAs[2]), is a major source of platinum associated with
   nickel ores in the Sudbury Basin deposit in Ontario, Canada. The rare
   sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with
   palladium and nickel. Cooperite occurs in the Merensky Reef within the
   Bushveld complex, Transvaal, South Africa. South Africa is the largest
   producer of platinum in the world.

   Platinum, often accompanied by small amounts of other platinum family
   metals, occurs in alluvial placer deposits in the Witwatersrand of
   South Africa, Colombia, Ontario, the Ural Mountains, and in certain
   western American states.

   Platinum is produced commercially as a by-product of nickel ore
   processing in the Sudbury deposit. The huge quantities of nickel ore
   processed makes up for the fact that platinum is present as only 0.5
   ppm in the ore.

Isotopes

   Naturally occurring platinum is composed of five stable isotopes and
   one radioisotope, Pt-190, which has a very long half-life (over 6
   billion years or 190 Ps). There are also many other radioisotopes with
   the most stable being Pt-193 with a half-life of 50 years.

Precautions

   According to the Centers for Disease Control and Prevention, short-term
   exposure to "platinum salts may cause irritation of the eyes, nose, and
   throat" and long-term exposure "may cause both respiratory and skin
   allergies." The current OSHA standard is 0.002 milligram per cubic
   meter of air averaged over an 8-hour work shift.

   Certain platinum complexes (cis-platin) have been used in chemotherapy,
   as they have very good anti-tumor activity, particularly when used to
   combat testicular cancer, although they also cause cumulative,
   irreversible kidney damage.

   As platinum is a catalyst in the manufacture of the silicone rubber and
   gel components of several types of medical implants (breast implants,
   joint replacement prosthetics, artificial lumbar discs, vascular access
   ports), the possibility that platinum free radicals could enter the
   body and cause adverse effects has merited study. However, the FDA has
   reviewed the issue and found no evidence to suggest toxicity in vivo. .

Rarity and colour

   Platinum's rarity as a metal has caused advertisers to associate it
   with exclusivity and wealth. "Platinum" credit cards have greater
   privileges than do "gold" ones. "Platinum awards" are the highest
   possible, ranking above gold, silver and bronze. For example, a musical
   album that has sold more than 1,000,000 copies, will be credited as
   "platinum" (a higher certification of " Diamond" does exist, however).
   And some products, such as blenders and vehicles, with a silvery-white
   colour are identified as "platinum". Platinum is considered a precious
   metal, although its use as such is not as common as the use of gold or
   silver. The frame of the Crown of Queen Elizabeth the Queen Mother,
   manufactured for her Coronation as Consort of King George VI, is made
   of platinum. It was the first British crown to be made of that metal.
   Due to its rarity, platinum is a highly priced metal, more so than gold
   or silver.

World production

   World supply of platinum is around 6 million troy ounces (190,000 kg)
   per year. Platinum's cost fluctuates around USD $1100 per ounce.
   Retrieved from " http://en.wikipedia.org/wiki/Platinum"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
