General | |||||||||||||||||||||||||
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Name, Symbol, Number | Iridium, Ir, 77 | ||||||||||||||||||||||||
Chemical series | transition metals | ||||||||||||||||||||||||
Group, Period, Block | 9[?], 6, d | ||||||||||||||||||||||||
Density, Hardness | 22650 kg/m3, 6.5 | ||||||||||||||||||||||||
Appearance | silvery white | ||||||||||||||||||||||||
Atomic Properties | |||||||||||||||||||||||||
Atomic weight | 192.217 amu | ||||||||||||||||||||||||
Atomic radius (calc.) | 135 (180) pm | ||||||||||||||||||||||||
Covalent radius | 137 pm | ||||||||||||||||||||||||
van der Waals radius | no data | ||||||||||||||||||||||||
Electron configuration | [Xe]4f14 5d7 6s2 | ||||||||||||||||||||||||
e- 's per energy level | 2, 8, 18, 32, 15, 2 | ||||||||||||||||||||||||
Oxidation states (Oxide) | 2, 3, 4, 6 (mildly basic) | ||||||||||||||||||||||||
Crystal structure | Cubic face centered | ||||||||||||||||||||||||
Physical Properties | |||||||||||||||||||||||||
State of matter | solid (__) | ||||||||||||||||||||||||
Melting point | 2739 K (4471 °F) | ||||||||||||||||||||||||
Boiling point | 4701 K (1962 °F) | ||||||||||||||||||||||||
Molar volume | 8.52 ×10-3 m3/mol | ||||||||||||||||||||||||
Heat of vaporization | 604 kJ/mol | ||||||||||||||||||||||||
Heat of fusion | 26.1 kJ/mol | ||||||||||||||||||||||||
Vapor pressure | 1.47 Pa at 2716 K | ||||||||||||||||||||||||
Speed of sound | 4825 m/s at 293.15 K | ||||||||||||||||||||||||
Miscellaneous | |||||||||||||||||||||||||
Electronegativity | 2.20 (Pauling scale) | ||||||||||||||||||||||||
Specific heat capacity | 130 J/(kg*K) | ||||||||||||||||||||||||
Electrical conductivity | 19.7 106/m ohm | ||||||||||||||||||||||||
Thermal conductivity | 147 W/(m*K) | ||||||||||||||||||||||||
1st ionization potential | 880 kJ/mol | ||||||||||||||||||||||||
2nd ionization potential | 1600 kJ/mol | ||||||||||||||||||||||||
Most Stable Isotopes | |||||||||||||||||||||||||
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SI units & STP are used except where noted. |
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Iridiuim can not be attacked by any acids or by aqua regia, but it can be attacked by molten salts, such as NaCl and NaCN. The specific gravity of this element is only slightly lower than osmium, which is generally considered to be the heaviest element known. However, calculations of density from the space lattice[?] may produce more reliable data for these elements than actual measurements and give a density of 22650 for iridium versus 22661 for osmium. Definitive selection between the two is therefore not possible at this time. It's just too close to call.
At one time iridium, as an alloy with platinum, was used in bushing the vents of heavy ordnance[?] and in a finely powdered condition (iridium black), for painting porcelain black.
This metal was to make the standard meter bar in Paris, which is an alloy of 90 % platinum and 10 % iridium. In 1960 the Paris meter bar was replaced as definition of the fundamental unit of length (see krypton).
The KT event, marking the temporal border between the Cretaceous and Tertiary eras of geological time, was identified by a thin stratum[?] of iridium. According to many scientists, such as Luis Alvarez of Berkeley, California, this iridium was of extraterrestrial origin, attributed to a comet thought to have struck near what is now the Yucatan Peninsula.
However, there are others such as Dewey M. McLean of Virginia Polytechnic Institute who argue that the iridium was of volcanic origin. The Earth's core is rich in iridium, and Piton de la Fournaise on Réunion, for example, is still releasing iridium today.
wikipedia.org dumped 2003-03-17 with terodump