Periodic Table of the Elements
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Bottom FACULTY OF CHEMICAL TECHNOLOGY o PERIODIC TABLE OF THE ELEMENTS Bottom
  A B C D E F G H I J K L M N O P R S T U V X Z  
Periodic Table of the Elements Tableau périodique des éléments Periodni sustav elemenata Tavola periodica degli elementi Das Periodensystem der Elemente
Iridium Iridium Iridij Iridio Iridium

 
Atomic number: 77
Group numbers: 9
Period: 6
 
Discovery date: 1803
Ir

Iridium
NEIGHBOURS
44
Ru
 45
Rh
 46
Pd
76
Os
 77
Ir
 78
Pt
108
Hs
 109
Mt
 


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Iridium was discovered by Smithson Tennant (England) in 1803. The origin of the name comes from the Latin word iris, meaning rainbow, because its salts are highly colored. It is heavy, brittle, white metal. Unreactive in air, water and acids. Attacked by fused NaOH. Metal ignites and burns readily.
Bottom TRANSITION ELEMENT: COBALT GROUP Top

Relative atomic mass: 192.217(3) Electronic configuration: [Xe] 4f14 5d7 6s2
Formal oxidation number: +3 +4 Electronegativities: 2.2
Thermal conductivity: 147 W m-1 K-1 Electrical resistivity (20 °C): 5.3 μΩcm
Atomic radius: 135.7 pm Standard state (20 °C): solid
Density (g dm-3): 22420 (290 K)
20000 (m.p.)		 Molar volume (cm3 mol-1): 8.57 (290 K)
8.74 (m.p.)


Bottom THERMAL PROPERTIES Top

Melting point: 2446 °C Heat of fusion: 26.4 kJ mol-1
Boiling point: 4428 °C Heat of vaporization: 612.1 kJ mol-1
Critical temperature: 7527 °C Heat of atomization: 664.34 kJ mol-1


Bottom IONIZATION ENERGIES AND ABUNDANCE Top

1st ionization energy: 865.19 kJ mol-1 Abundance of element (air): - ppm
2nd ionization energy: - kJ mol-1 Abundance of element (Earth's crust): 0.0001 ppm
3rd ionization energy: - kJ mol-1 Abundance of element (oceans): - ppm


Bottom ISOTOPES Top

Isotopes Relative atomic mass Abundance (%)
191Ir190.960591(3)37.3(5)
193Ir192.962924(3)62.7(5)


Bottom MINERALS AND USES Top

Iridium is found in gravel deposits with platinum. Used with osmium to tip gold pen points, to make crucible and special containers. Also to make alloys used for standard weights and measures and heat-resistant alloys. Also as hardening agent for platinum. The price of 99.95 % pure iridium sponge is 829.60 € for 10 g.

Bottom REDUCTION POTENTIALS Top

Balanced half-reaction   Eo / V      Annotation
Ir3+ + 3e- = Ir(s) +1.15  
IrCl62- + e- = IrCl63- +1.026  
IrCl62- + 4e- = Ir(s) + 6Cl- +0.835  
IrCl63- + 3e- = Ir(s) + 6Cl- +0.77  
IrO2(s) + 4H+ + 4e- = Ir(s) + H2O +0.93  
IrO2(s) + 2H2O + 4e- = Ir(s) + 4OH- +0.1  
Ir2O3 + 3H2O + 6e- = 2Ir(s) + 6OH- +0.1  

 

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