Iridium

Iridium (Ir)

Very hard and brittle, silvery metallic transition element. It has a yellowish cast to it. Salts of iridium are highly colored. It is the most corrosion resistant metal known, not attacked by any acid, but is attacked by molten salts. There are two natural isotopes of iridium, and 4 radioisotopes, the most stable being Ir-192 with a half-life of 73.83 days. Ir-192 decays into Platinum, while the other radioisotopes decay into Osmium. Iridium is used in high temperature apparatus, electrical contacts, and as a hardening agent for platinumpy. Discovered in 1803 by Smithson Tennant in England. The name comes from the Greek word iris, which means rainbow. Iridium metal is generally non-toxic due to its relative unreactivity, but iridium compounds should be considered highly toxic.
Atomic Number77
Atomic Weight192.217
Mass Number193
Group9
Period6
Blockd
Protons77 p+
Neutrons116 n0
Electrons77 e-
Iridium foil.jpg Animated Bohr Model of Ir (Iridium) Enhanced Bohr Model of Ir (Iridium) Bohr Model: Ir (Iridium) Orbital Diagram of Ir (Iridium)

Properties

Atomic Radius
135 pm
Molar Volume
Covalent Radius
122 pm
Metallic Radius
127 pm
Ionic Radius
68 pm
Crystal Radius
82 pm
Van der Waals Radius
213 pm
Density
22.5622 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy
8.96702 eV/particle
Heat of Vaporization
604 kJ/mol
Heat of Fusion
27.61 kJ/mol
Heat of Formation
669 kJ/mol
Electrons
Electron Shells2, 8, 18, 32, 15, 2
Valence Electrons6
Electron Configuration[Xe] 4f14 5d7 6s2
Oxidation States-3, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Electronegativity
2.2
Electrophilicity
1.872465121129725 eV/particle
Phases
PhaseSolid
Gas Phase
Boiling Point
4,701.15 K
Melting Point
2,719.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Silver
Appearancesilvery white
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
0.0000064 1/K
Molar Heat Capacity
Specific Heat Capacity
0.131 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
TypeConductor
Electrical Conductivity
21 MS/m
Electrical Resistivity
0.00000004699999999998 m Ω
Superconducting Point
0.11 K
Magnetism
Typeparamagnetic
Magnetic Susceptibility (Mass)
0.00000000167 m³/Kg
Magnetic Susceptibility (Molar)
0.000000000321 m³/mol
Magnetic Susceptibility (Volume)
0.0000377
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal StructureFace Centered Cubic (FCC)
Lattice Constant
3.84 Å
Lattice Anglesπ/2, π/2, π/2
Mechanical Properties
Hardness
6.5 MPa
Bulk Modulus
320 GPa
Shear Modulus
210 GPa
Young Modulus
528 GPa
Poisson Ratio
0.26
Speed of Sound
4,825 m/s
Classification
CategoryTransition metals, Transition metals
CAS GroupVIIIA
IUPAC GroupVIII
Glawe Number62
Mendeleev Number65
Pettifor Number65
Geochemical Classnoble metal
Goldschmidt Classsiderophile
Other
Gas Basicity
Dipole Polarizability
54 ± 7 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section
425
Neutron Mass Absorption
0.081
Quantum Numbers4F9/2
Space Group225 (Fm_3m)

Isotopes of Iridium

Stable Isotopes2
Unstable Isotopes41
Radioactive Isotopes40

163Ir

Abundance
Relative Atomic Mass
162.994299 ± 0.000429 Da
Mass Number163
G-Factor
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year
Parity+

163Ir Decay Modes
Decay ModeIntensity
p (proton emission)%

164Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
163.991966 ± 0.000339 Da
Mass Number164
G-Factor
Half Life
Spin2
Quadrupole Moment
Discovery Year
Parity-

164Ir Decay Modes
Decay ModeIntensity
p (proton emission)%
α (α emission)%
β+ (β+ decay; β+ = ϵ + e+)%

165Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
164.987552 ± 0.00017 Da
Mass Number165
G-Factor
Half Life
Spin1/2
Quadrupole Moment
0
Discovery Year
Parity+

165Ir Decay Modes
Decay ModeIntensity
p (proton emission)%
α (α emission)%

166Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
165.985716 ± 0.000215 Da
Mass Number166
G-Factor
Half Life
10.5 ± 2.2 ms
Spin2
Quadrupole Moment
Discovery Year1981
Parity

166Ir Decay Modes
Decay ModeIntensity
α (α emission)93%
p (proton emission)7%

167Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
166.981671973 ± 0.000019694 Da
Mass Number167
G-Factor
Half Life
29.3 ± 0.6 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1981
Parity+

167Ir Decay Modes
Decay ModeIntensity
α (α emission)43.5%
p (proton emission)38.6%
β+ (β+ decay; β+ = ϵ + e+)%

168Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
167.979960978 ± 0.000059277 Da
Mass Number168
G-Factor
Half Life
230 ± 50 ms
Spin2
Quadrupole Moment
Discovery Year1978
Parity

168Ir Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%
β+ p (β+-delayed proton emission)%

169Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
168.976281743 ± 0.00002502 Da
Mass Number169
G-Factor
Half Life
353 ± 4 ms
Spin1/2
Quadrupole Moment
0
Discovery Year1978
Parity+

169Ir Decay Modes
Decay ModeIntensity
α (α emission)53%
β+ (β+ decay; β+ = ϵ + e+)%

170Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
169.975113 ± 0.000109 Da
Mass Number170
G-Factor
Half Life
910 ± 150 ms
Spin3
Quadrupole Moment
Discovery Year1977
Parity-

170Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)%
α (α emission)5.2%

171Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
170.97164552 ± 0.000041295 Da
Mass Number171
G-Factor
Half Life
3.1 ± 0.3 s
Spin1/2
Quadrupole Moment
0
Discovery Year1967
Parity+

171Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)%
α (α emission)15%

172Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
171.970607035 ± 0.000034785 Da
Mass Number172
G-Factor
Half Life
4.4 ± 0.3 s
Spin3
Quadrupole Moment
Discovery Year1967
Parity-

172Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)98%
α (α emission)2%

173Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
172.967505477 ± 0.000011316 Da
Mass Number173
G-Factor
Half Life
9 ± 0.8 s
Spin1/2
Quadrupole Moment
0
Discovery Year1967
Parity+

173Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)96.5%
α (α emission)3.5%

174Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
173.966949939 ± 0.000012046 Da
Mass Number174
G-Factor
Half Life
7.9 ± 0.6 s
Spin2
Quadrupole Moment
Discovery Year1967
Parity+

174Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)99.5%
α (α emission)0.5%

175Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
174.964149519 ± 0.000013295 Da
Mass Number175
G-Factor
Half Life
9 ± 2 s
Spin1/2
Quadrupole Moment
0
Discovery Year1967
Parity+

175Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)99.15%
α (α emission)0.85%

176Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
175.963626261 ± 0.000008679 Da
Mass Number176
G-Factor
Half Life
8.7 ± 0.5 s
Spin3
Quadrupole Moment
Discovery Year1967
Parity+

176Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)96.9%
α (α emission)3.1%

177Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
176.9613015 ± 0.000021213 Da
Mass Number177
G-Factor
Half Life
29.8 ± 1.7 s
Spin5/2
Quadrupole Moment
Discovery Year1967
Parity-

177Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)0.06%

178Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
177.961079395 ± 0.000020204 Da
Mass Number178
G-Factor
Half Life
12 ± 2 s
Spin3
Quadrupole Moment
Discovery Year1972
Parity+

178Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

179Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
178.959117594 ± 0.000010489 Da
Mass Number179
G-Factor
Half Life
79 ± 1 s
Spin5/2
Quadrupole Moment
Discovery Year1992
Parity

179Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

180Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
179.959229446 ± 0.000023302 Da
Mass Number180
G-Factor
0.5 ± 0.04
Half Life
1.5 ± 0.1 m
Spin5
Quadrupole Moment
Discovery Year1972
Parity+

180Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

181Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
180.957634691 ± 0.000005631 Da
Mass Number181
G-Factor
Half Life
4.9 ± 0.15 m
Spin5/2
Quadrupole Moment
Discovery Year1972
Parity-

181Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

182Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
181.958076296 ± 0.000022509 Da
Mass Number182
G-Factor
Half Life
15 ± 1 m
Spin3
Quadrupole Moment
Discovery Year1961
Parity+

182Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

183Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
182.956841231 ± 0.000026486 Da
Mass Number183
G-Factor
Half Life
58 ± 5 m
Spin5/2
Quadrupole Moment
Discovery Year1961
Parity-

183Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)%

184Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
183.957476 ± 0.00003 Da
Mass Number184
G-Factor
Half Life
3.09 ± 0.03 h
Spin5
Quadrupole Moment
2.41 ± 0.03
Discovery Year1960
Parity-

184Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

185Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
184.956698 ± 0.00003 Da
Mass Number185
G-Factor
1.0384 ± 0.0052
Half Life
14.4 ± 0.1 h
Spin5/2
Quadrupole Moment
Discovery Year1958
Parity-

185Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

186Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
185.957946754 ± 0.00001774 Da
Mass Number186
G-Factor
Half Life
16.64 ± 0.03 h
Spin5
Quadrupole Moment
-2.55 ± 0.03
Discovery Year1958
Parity+

186Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

187Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
186.957542 ± 0.00003 Da
Mass Number187
G-Factor
Half Life
10.5 ± 0.3 h
Spin3/2
Quadrupole Moment
0.941 ± 0.011
Discovery Year1958
Parity+

187Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

188Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
187.958834999 ± 0.000010116 Da
Mass Number188
G-Factor
Half Life
41.5 ± 0.5 h
Spin1
Quadrupole Moment
0.484 ± 0.006
Discovery Year1950
Parity-

188Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%

189Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
188.958722602 ± 0.0000135 Da
Mass Number189
G-Factor
Half Life
13.2 ± 0.1 d
Spin3/2
Quadrupole Moment
Discovery Year1955
Parity+

189Ir Decay Modes
Decay ModeIntensity
ϵ (electron capture)100%

190Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
189.960543374 ± 0.00000147 Da
Mass Number190
G-Factor
0.01 ± 0.0025
Half Life
11.78 ± 0.1 d
Spin4
Quadrupole Moment
2.87 ± 0.16
Discovery Year1947
Parity-

190Ir Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
e+ (positron emission)0.002%

191Ir

Abundance
37.3 ± 0.2
Relative Atomic Mass
190.960591455 ± 0.000001406 Da
Mass Number191
G-Factor
0.10013333333333 ± 0.0004
Half Life
Spin3/2
Quadrupole Moment
0.816 ± 0.009
Discovery Year1935
Parity+

192Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
191.962602414 ± 0.00000141 Da
Mass Number192
G-Factor
0.47925 ± 0.0025
Half Life
73.82 ± 0.014 d
Spin4
Quadrupole Moment
2.15 ± 0.06
Discovery Year1937
Parity+

192Ir Decay Modes
Decay ModeIntensity
β (β decay)95.24%
ϵ (electron capture)4.76%

193Ir

Abundance
62.7 ± 0.2
Relative Atomic Mass
192.962923753 ± 0.000001425 Da
Mass Number193
G-Factor
0.10866666666667 ± 0.0004
Half Life
Spin3/2
Quadrupole Moment
0.751 ± 0.009
Discovery Year1935
Parity+

194Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
193.965075703 ± 0.000001429 Da
Mass Number194
G-Factor
0.39 ± 0.01
Half Life
19.35 ± 0.07 h
Spin1
Quadrupole Moment
0.339 ± 0.012
Discovery Year1937
Parity-

194Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

195Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
194.965976898 ± 0.000001431 Da
Mass Number195
G-Factor
Half Life
2.29 ± 0.17 h
Spin3/2
Quadrupole Moment
Discovery Year1952
Parity+

195Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

196Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
195.968399669 ± 0.000041239 Da
Mass Number196
G-Factor
Half Life
52 ± 1.1 s
Spin1
Quadrupole Moment
Discovery Year1966
Parity

196Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

197Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
196.969657217 ± 0.000021588 Da
Mass Number197
G-Factor
Half Life
5.8 ± 0.5 m
Spin3/2
Quadrupole Moment
Discovery Year1952
Parity+

197Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

198Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
197.972399 ± 0.000215 Da
Mass Number198
G-Factor
Half Life
8.7 ± 0.4 s
Spin1
Quadrupole Moment
Discovery Year1973
Parity-

198Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

199Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
198.973807097 ± 0.000044073 Da
Mass Number199
G-Factor
Half Life
7 ± 5 s
Spin3/2
Quadrupole Moment
Discovery Year1993
Parity+

199Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

200Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
199.976844 ± 0.00021 Da
Mass Number200
G-Factor
Half Life
43 ± 6 s
Spin2
Quadrupole Moment
Discovery Year2008
Parity-

200Ir Decay Modes
Decay ModeIntensity
β (β decay)100%
β n (β-delayed neutron emission)%

201Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
200.978701 ± 0.000215 Da
Mass Number201
G-Factor
Half Life
21 ± 5 s
Spin3/2
Quadrupole Moment
Discovery Year2008
Parity+

201Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

202Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
201.982136 ± 0.000322 Da
Mass Number202
G-Factor
Half Life
11 ± 3 s
Spin2
Quadrupole Moment
Discovery Year2008
Parity-

202Ir Decay Modes
Decay ModeIntensity
β (β decay)100%

203Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
202.984573 ± 0.000429 Da
Mass Number203
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year2009
Parity+

203Ir Decay Modes
Decay ModeIntensity
β (β decay)%

204Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
203.989726 ± 0.000429 Da
Mass Number204
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year2011
Parity

204Ir Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%

205Ir

AbundanceRadioactive ☢️
Relative Atomic Mass
204.993988 ± 0.000537 Da
Mass Number205
G-Factor
Half Life
Spin3/2
Quadrupole Moment
Discovery Year2012
Parity+

205Ir Decay Modes
Decay ModeIntensity
β (β decay)%
β n (β-delayed neutron emission)%

History

Iridium was discovered in 1803 by English chemist Smithson Tennant in London. Chemists who studied platinum dissolved it in aqua regia to create soluble salts and observed a small amount of a dark, insoluble residue. Smithson Tennant analyzed the insoluble residue and concluded that it must contain a new metal. From the Latin word iris meaning rainbow

DiscoverersS.Tenant, A.F.Fourcory, L.N.Vauquelin, H.V.Collet-Descoltils
Discovery LocationEngland/France
Discovery Year1804
Etymology (Name Origin)Latin: iris (rainbow).
Pronunciationi-RID-i-em (English)
Iridium is considered to be of low toxicity
Iridium is the most corrosion-resistant metal known

Uses

Iridium is used in making crucibles and other equipment that is used at high temperatures. Iridium is also used as a hardening agent in platinum alloys. Its resistance to arc erosion makes iridium alloys ideal for electrical contacts for spark plugs. Radioactive isotopes of iridium are used in radiation therapy for the treatment of cancer. 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.

Sources

Found in gravel deposits with platinum.

Abundance
Abundance in Earth's crust
0.001 mg/kg
Abundance in Oceans
Abundance in Human Body
Abundance in Meteor
0.000054 %
Abundance in Sun
0.0000002 %
Abundance in Universe
0.0000002 %

Nuclear Screening Constants

1s1.4881
2p4.4624
2s20.1102
3d13.514
3p21.9311
3s22.7942
4d37.2628
4f38.6552
4p35.086
4s34.152
5d58.304
5p53.339
5s51.1545
6s66.4334