Difference between revisions of "Iridium"
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{{Infobox element | {{Infobox element | ||
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| − | |image name= | + | |image name=Iridium granules at Johnson Matthey noble metal plant.jpg |
|image alt= | |image alt= | ||
|image size= | |image size= | ||
| − | |image name comment= | + | |image name comment=Iridium metal granules in the hands of prof. Martyn Poliakoff |
|image name 2= | |image name 2= | ||
|image alt 2= | |image alt 2= | ||
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|phase ref= | |phase ref= | ||
|phase comment= | |phase comment= | ||
| − | |melting point K= | + | |melting point K=2719 |
| − | |melting point C= | + | |melting point C=2446 |
| − | |melting point F= | + | |melting point F=4435 |
|melting point ref= | |melting point ref= | ||
|melting point comment= | |melting point comment= | ||
| − | |boiling point K= | + | |boiling point K=4403 |
| − | |boiling point C= | + | |boiling point C=4130 |
| − | |boiling point F= | + | |boiling point F=7466 |
|boiling point ref= | |boiling point ref= | ||
|boiling point comment= | |boiling point comment= | ||
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|density gplstp ref= | |density gplstp ref= | ||
|density gplstp comment= | |density gplstp comment= | ||
| − | |density gpcm3nrt= | + | |density gpcm3nrt=22.56 |
|density gpcm3nrt ref= | |density gpcm3nrt ref= | ||
|density gpcm3nrt comment= | |density gpcm3nrt comment= | ||
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|density gpcm3nrt 3 ref= | |density gpcm3nrt 3 ref= | ||
|density gpcm3nrt 3 comment= | |density gpcm3nrt 3 comment= | ||
| − | |density gpcm3mp= | + | |density gpcm3mp=19 |
|density gpcm3mp ref= | |density gpcm3mp ref= | ||
|density gpcm3mp comment= | |density gpcm3mp comment= | ||
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|critical point ref= | |critical point ref= | ||
|critical point comment= | |critical point comment= | ||
| − | |heat fusion= | + | |heat fusion=41.12 |
|heat fusion ref= | |heat fusion ref= | ||
|heat fusion comment= | |heat fusion comment= | ||
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|heat fusion 2 ref= | |heat fusion 2 ref= | ||
|heat fusion 2 comment= | |heat fusion 2 comment= | ||
| − | |heat vaporization= | + | |heat vaporization=564 |
|heat vaporization ref= | |heat vaporization ref= | ||
|heat vaporization comment= | |heat vaporization comment= | ||
| − | |heat capacity= | + | |heat capacity=25.1 |
|heat capacity ref= | |heat capacity ref= | ||
|heat capacity comment= | |heat capacity comment= | ||
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|heat capacity 2 ref= | |heat capacity 2 ref= | ||
|heat capacity 2 comment= | |heat capacity 2 comment= | ||
| − | |vapor pressure 1= | + | |vapor pressure 1=2713 |
| − | |vapor pressure 10= | + | |vapor pressure 10=2957 |
| − | |vapor pressure 100= | + | |vapor pressure 100=3252 |
| − | |vapor pressure 1 k= | + | |vapor pressure 1 k=3614 |
| − | |vapor pressure 10 k= | + | |vapor pressure 10 k=4069 |
| − | |vapor pressure 100 k= | + | |vapor pressure 100 k=4659 |
|vapor pressure ref= | |vapor pressure ref= | ||
|vapor pressure comment= | |vapor pressure comment= | ||
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<!-- Atomic properties --> | <!-- Atomic properties --> | ||
|atomic properties comment= | |atomic properties comment= | ||
| − | |oxidation states= | + | |oxidation states=−3, −1, 0, 1, 2, '''3''', '''4''', 5, 6, 7, 8, 9 |
|oxidation states ref= | |oxidation states ref= | ||
|oxidation states comment= | |oxidation states comment= | ||
| − | |electronegativity= | + | |electronegativity=2.20 |
|electronegativity ref= | |electronegativity ref= | ||
|electronegativity comment= | |electronegativity comment= | ||
| − | |ionization energy 1= | + | |ionization energy 1=880 |
|ionization energy 1 ref= | |ionization energy 1 ref= | ||
|ionization energy 1 comment= | |ionization energy 1 comment= | ||
| − | |ionization energy 2= | + | |ionization energy 2=1600 |
|ionization energy 2 ref= | |ionization energy 2 ref= | ||
|ionization energy 2 comment= | |ionization energy 2 comment= | ||
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|ionization energy ref= | |ionization energy ref= | ||
|ionization energy comment= | |ionization energy comment= | ||
| − | |atomic radius= | + | |atomic radius=136 |
|atomic radius ref= | |atomic radius ref= | ||
|atomic radius comment= | |atomic radius comment= | ||
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|atomic radius calculated ref= | |atomic radius calculated ref= | ||
|atomic radius calculated comment= | |atomic radius calculated comment= | ||
| − | |covalent radius= | + | |covalent radius=141±6 |
|covalent radius ref= | |covalent radius ref= | ||
|covalent radius comment= | |covalent radius comment= | ||
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|crystal structure prefix= | |crystal structure prefix= | ||
|crystal structure ref= | |crystal structure ref= | ||
| − | |crystal structure comment= | + | |crystal structure comment=Face-centered cubic (fcc) |
|crystal structure 2= | |crystal structure 2= | ||
|crystal structure 2 prefix= | |crystal structure 2 prefix= | ||
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|speed of sound ref= | |speed of sound ref= | ||
|speed of sound comment= | |speed of sound comment= | ||
| − | |speed of sound rod at 20= | + | |speed of sound rod at 20=4825 |
|speed of sound rod at 20 ref= | |speed of sound rod at 20 ref= | ||
|speed of sound rod at 20 comment= | |speed of sound rod at 20 comment= | ||
| Line 185: | Line 185: | ||
|speed of sound rod at r.t. ref= | |speed of sound rod at r.t. ref= | ||
|speed of sound rod at r.t. comment= | |speed of sound rod at r.t. comment= | ||
| − | |thermal expansion= | + | |thermal expansion=6.4 |
|thermal expansion ref= | |thermal expansion ref= | ||
|thermal expansion comment= | |thermal expansion comment= | ||
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|thermal expansion at 25 ref= | |thermal expansion at 25 ref= | ||
|thermal expansion at 25 comment= | |thermal expansion at 25 comment= | ||
| − | |thermal conductivity= | + | |thermal conductivity=147 |
|thermal conductivity ref= | |thermal conductivity ref= | ||
|thermal conductivity comment= | |thermal conductivity comment= | ||
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|electrical resistivity at 0 ref= | |electrical resistivity at 0 ref= | ||
|electrical resistivity at 0 comment= | |electrical resistivity at 0 comment= | ||
| − | |electrical resistivity at 20= | + | |electrical resistivity at 20=4.71·10<sup>-8</sup> |
|electrical resistivity at 20 ref= | |electrical resistivity at 20 ref= | ||
|electrical resistivity at 20 comment= | |electrical resistivity at 20 comment= | ||
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|Curie point ref= | |Curie point ref= | ||
|Curie point comment= | |Curie point comment= | ||
| − | |magnetic ordering= | + | |magnetic ordering=Paramagnetic |
|magnetic ordering ref= | |magnetic ordering ref= | ||
|magnetic ordering comment= | |magnetic ordering comment= | ||
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|tensile strength ref= | |tensile strength ref= | ||
|tensile strength comment= | |tensile strength comment= | ||
| − | |Young's modulus= | + | |Young's modulus=528 |
|Young's modulus ref= | |Young's modulus ref= | ||
|Young's modulus comment= | |Young's modulus comment= | ||
| − | |Shear modulus= | + | |Shear modulus=210 |
|Shear modulus ref= | |Shear modulus ref= | ||
|Shear modulus comment= | |Shear modulus comment= | ||
| − | |Bulk modulus= | + | |Bulk modulus=320 |
|Bulk modulus ref= | |Bulk modulus ref= | ||
|Bulk modulus comment= | |Bulk modulus comment= | ||
| − | |Poisson ratio= | + | |Poisson ratio=0.26 |
|Poisson ratio ref= | |Poisson ratio ref= | ||
|Poisson ratio comment= | |Poisson ratio comment= | ||
| − | |Mohs hardness= | + | |Mohs hardness=6.5 |
|Mohs hardness ref= | |Mohs hardness ref= | ||
|Mohs hardness comment= | |Mohs hardness comment= | ||
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|Mohs hardness 2 ref= | |Mohs hardness 2 ref= | ||
|Mohs hardness 2 comment= | |Mohs hardness 2 comment= | ||
| − | |Vickers hardness= | + | |Vickers hardness=1760–2200 |
|Vickers hardness ref= | |Vickers hardness ref= | ||
|Vickers hardness comment= | |Vickers hardness comment= | ||
| − | |Brinell hardness= | + | |Brinell hardness=1670 |
|Brinell hardness ref= | |Brinell hardness ref= | ||
|Brinell hardness comment= | |Brinell hardness comment= | ||
| − | |CAS number= | + | |CAS number=7439-88-5 |
|CAS number ref= | |CAS number ref= | ||
|CAS number comment= | |CAS number comment= | ||
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|first isolation date ref= | |first isolation date ref= | ||
|first isolation date= | |first isolation date= | ||
| − | |discovery and first isolation by= | + | |discovery and first isolation by=Smithson Tennant (1803) |
|named by= | |named by= | ||
|named date ref= | |named date ref= | ||
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==Properties== | ==Properties== | ||
===Chemical=== | ===Chemical=== | ||
| − | Iridium is the most corrosion resistant metal, even at high temperatures. At standard conditions, no chemical compound can attack it. Finely divided however, it is more reactive. At high temperatures, molten [[sodium cyanide]] and [[potassium cyanide]] will attack iridium, as well as [[oxygen]] and [[fluorine]]. | + | Iridium is the most corrosion resistant metal, even at high temperatures. At standard conditions, no chemical compound can attack it in bulk form. Finely divided however, it is more reactive. At high temperatures, molten [[sodium cyanide]] and [[potassium cyanide]] will attack iridium, as well as [[oxygen]] and [[fluorine]]. |
Iridium tends to form mixed-valence compounds, most notably [[iridum(IV) chloride]] (whose name is particularly unusual). | Iridium tends to form mixed-valence compounds, most notably [[iridum(IV) chloride]] (whose name is particularly unusual). | ||
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==Availability== | ==Availability== | ||
| − | In nature it usually found together with osmium, usually in meteorites. However due to | + | In nature it usually found together with osmium, usually in meteorites. However due to the low concentration of Ir in meteorites and rarity of intact meteorites in nature, space rocks are not a particularly good source for the amateur chemist. |
| − | Iridium can be found in certain high-performance car spark plugs, in the tip of the electric contact. Because it's immune to most corrosive substances, it's recommended to dissolve the welding around the iridium. It is not much, but being very dense, just a few spark tips can build up a significant quantity. | + | Iridium can be found in certain high-performance car spark plugs, in the tip of the electric contact. Because it's immune to most corrosive substances, it's recommended to dissolve the welding around the iridium, with a strong acid. It is not much, but being very dense, just a few spark tips can build up a significant quantity. |
| − | Lastly, iridium can be bought as bullions and coins, though in recent years | + | Lastly, iridium can be bought as bullions and coins, though in recent years its price has risen to 46 $/gram. |
| − | Iridium's high melting point and chemical resistance allows it to be used in the creation of high-performance crucibles which, unlike the ceramic ones, are very thin, thus reducing the amount of iridium used. Such crucibles are used for single crystal growth. | + | Iridium's high melting point and chemical resistance allows it to be used in the creation of high-performance crucibles which, unlike the ceramic ones, are very thin, thus reducing the amount of iridium used. Such crucibles are widely used for single crystal growth. |
==Preparation== | ==Preparation== | ||
Latest revision as of 16:56, 2 November 2022
 Iridium metal granules in the hands of prof. Martyn Poliakoff | |||||
| General properties | |||||
|---|---|---|---|---|---|
| Name, symbol | Iridium, Ir | ||||
| Appearance | Silvery shiny metal | ||||
| Iridium in the periodic table | |||||
| |||||
| Atomic number | 77 | ||||
| Standard atomic weight (Ar) | 192.217(3) | ||||
| Group, block | , d-block | ||||
| Period | period 6 | ||||
| Electron configuration | [Xe] 4f14 5d7 6s2 | ||||
per shell | 2, 8, 18, 32, 15, 2 | ||||
| Physical properties | |||||
| Silvery-white | |||||
| Phase | Solid | ||||
| Melting point | 2719 K (2446 °C, 4435 °F) | ||||
| Boiling point | 4403 K (4130 °C, 7466 °F) | ||||
| Density near r.t. | 22.56 g/cm3 | ||||
| when liquid, at | 19 g/cm3 | ||||
| Heat of fusion | 41.12 kJ/mol | ||||
| Heat of | 564 kJ/mol | ||||
| Molar heat capacity | 25.1 J/(mol·K) | ||||
| pressure | |||||
| Atomic properties | |||||
| Oxidation states | −3, −1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 | ||||
| Electronegativity | Pauling scale: 2.20 | ||||
| energies |
1st: 880 kJ/mol 2nd: 1600 kJ/mol | ||||
| Atomic radius | empirical: 136 pm | ||||
| Covalent radius | 141±6 pm | ||||
| Miscellanea | |||||
| Crystal structure | Face-centered cubic (fcc) | ||||
| Speed of sound thin rod | 4825 m/s (at 20 °C) | ||||
| Thermal expansion | 6.4 µm/(m·K) | ||||
| Thermal conductivity | 147 W/(m·K) | ||||
| Electrical resistivity | 4.71·10-8 Ω·m (at 20 °C) | ||||
| Magnetic ordering | Paramagnetic | ||||
| Young's modulus | 528 GPa | ||||
| Shear modulus | 210 GPa | ||||
| Bulk modulus | 320 GPa | ||||
| Poisson ratio | 0.26 | ||||
| Mohs hardness | 6.5 | ||||
| Vickers hardness | 1760–2200 MPa | ||||
| Brinell hardness | 1670 MPa | ||||
| CAS Registry Number | 7439-88-5 | ||||
| Discovery and first isolation | Smithson Tennant (1803) | ||||
Iridium is the chemical element with symbol Ir and atomic number 77. It is a transitional group metal, part of the so called platinum group metals. Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only three metric tonnes, making it an expensive metal. However, despite the fact that iridium is rarer than platinum and gold, it is somewhat cheaper due to peculiarities of the precious metal market.
Contents
Properties
Chemical
Iridium is the most corrosion resistant metal, even at high temperatures. At standard conditions, no chemical compound can attack it in bulk form. Finely divided however, it is more reactive. At high temperatures, molten sodium cyanide and potassium cyanide will attack iridium, as well as oxygen and fluorine.
Iridium tends to form mixed-valence compounds, most notably iridum(IV) chloride (whose name is particularly unusual).
Iridium will form alloys with metals, such as osmium (osmiridium) and iron.
Iridium's organometallic chemistry is extensively studied, as iridium forms very stable bonds with carbon.
Physical
Iridium is a silvery white, very hard metal. It has excellent mechanical properties, which makes it difficult to work with. It's high melting point of 2446 °C makes it difficult to melt and cast, so powdered metallurgy is usually employed. It is the only metal to maintain good mechanical properties in air at temperatures above 1600 °C, making it useful as a high temperature catalyst. It is the second densest element after osmium, with a value of 22.56 g/cm3. Because of this property, most of the elemental iridium has sunk in the Earth crust.
Availability
In nature it usually found together with osmium, usually in meteorites. However due to the low concentration of Ir in meteorites and rarity of intact meteorites in nature, space rocks are not a particularly good source for the amateur chemist.
Iridium can be found in certain high-performance car spark plugs, in the tip of the electric contact. Because it's immune to most corrosive substances, it's recommended to dissolve the welding around the iridium, with a strong acid. It is not much, but being very dense, just a few spark tips can build up a significant quantity.
Lastly, iridium can be bought as bullions and coins, though in recent years its price has risen to 46 $/gram.
Iridium's high melting point and chemical resistance allows it to be used in the creation of high-performance crucibles which, unlike the ceramic ones, are very thin, thus reducing the amount of iridium used. Such crucibles are widely used for single crystal growth.
Preparation
As it sits at the bottom of the metal reactivity series, it can be reduced very easy from it's compounds.
Projects
- Organoiridium compounds
- Single crystal growth in iridium crucibles
Handling
Safety
Being the least reactive metal, iridium is non-toxic. Finely divided iridium powder can be hazardous to handle, as it is an irritant and may ignite in air.
Storage
Bulk iridium does not require any special storage. Powdered iridium should be stored in closed containers.
Disposal
Due to iridium's rarity and price, it's best to recycle it.
