Iridium Element Information, Facts, Properties, Trends, Uses, Comparison with other elements
Iridium is a chemical element with symbol Ir and atomic number 77. A very hard, brittle, silvery-white Transition Metal of the platinum group, iridium is generally credited with being the second densest element (after osmium) based on measured density, although calculations involving the space lattices of the elements show that iridium is denser. It is also the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts and Halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.
It belongs to group 9 of the periodic table having trivial name null. You can also download Printable Periodic Table of Elements Flashcards for Iridium in a PDF format.
Iridium Facts
Read key information and facts about element Iridium
| Name | Iridium |
| Atomic Number | 77 |
| Atomic Symbol | Ir |
| Atomic Weight | 192.217 |
| Phase | Solid |
| Color | Silver |
| Appearance | silvery white |
| Classification | Transition Metal |
| Natural Occurance | Primordial |
| Group in Periodic Table | 9 |
| Group Name | cobalt family |
| Period in Periodic Table | period 6 |
| Block in Periodic Table | d-block |
| Electronic Configuration | [Xe] 4f14 5d7 6s2 |
| Electronic Shell Structure (Electrons per shell) | 2, 8, 18, 32, 15, 2 |
| Melting Point | 2739 K |
| Boiling Point | 4701 K |
| CAS Number | CAS7439-88-5 |
How to Locate Iridium on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 77 to find Iridium on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Iridium on periodic table look for cross section of group 9 and period 6 in the modern periodic table.
Iridium History
The element Iridium was discovered by S. Tennant in year 1803 in France and United Kingdom. Iridium was first isolated by S. Tennant in 1803. Iridium derived its name from Iris, the Greek goddess of the rainbow.
| Discovered By | S. Tennant |
| Discovery Date | 1803 in France and United Kingdom |
| First Isolation | 1803 |
| Isolated by | S. Tennant |
Tennant had been working on samples of South American platinum in parallel with Wollaston and discovered two new elements, which he named osmium and iridium, and published the iridium results in 1804.
Iridium Uses
Iridium is mostly used as a hardening agent for platinum. This element is also used as an alloy in fountain pen tips and compass bearings, and for the contacts in spark plugs.
Iridium Presence: Abundance in Nature and Around Us
The table below shows the abundance of Iridium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
| ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
|---|---|---|
| Abundance in Universe | 2 | 0.01 |
| Abundance in Sun | 2 | 0.01 |
| Abundance in Meteorites | 550 | 60 |
| Abundance in Earth's Crust | 0.4 | 0.05 |
| Abundance in Oceans | - | - |
| Abundance in Humans | - | - |
Crystal Structure of Iridium
The solid state structure of Iridium is Face Centered Cubic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
| a | b | c |
|---|---|---|
| 383.9 pm | 383.9 pm | 383.9 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
| alpha | beta | gamma |
|---|---|---|
| π/2 | π/2 | π/2 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
| Space Group Name | Fm_ 3m |
| Space Group Number | 225 |
| Crystal Structure | Face Centered Cubic |
| Number of atoms per unit cell | 4 |
The number of atoms per unit cell in a simple cubic, face-centered cubic and body-centred cubic are 1,4,2 respectively.
Iridium Atomic and Orbital Properties
Iridium atoms have 77 electrons and the electronic shell structure is [2, 8, 18, 32, 15, 2] with Atomic Term Symbol (Quantum Numbers) 4F9/2.
| Atomic Number | 77 |
| Number of Electrons (with no charge) | 77 |
| Number of Protons | 77 |
| Mass Number | 192 |
| Number of Neutrons | 115 |
| Shell structure (Electrons per energy level) | 2, 8, 18, 32, 15, 2 |
| Electron Configuration | [Xe] 4f14 5d7 6s2 |
| Valence Electrons | 5d7 6s2 |
| Valence (Valency) | 6 |
| Main Oxidation States | 3, 4 |
| Oxidation States | -3, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 |
| Atomic Term Symbol (Quantum Numbers) | 4F9/2 |
Bohr Atomic Model of Iridium - Electrons per energy level
| n | s | p | d | f |
|---|
Ground State Electronic Configuration of Iridium - neutral Iridium atom
Abbreviated electronic configuration of Iridium
The ground state abbreviated electronic configuration of Neutral Iridium atom is [Xe] 4f14 5d7 6s2. The portion of Iridium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Xe]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 5d7 6s2, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Iridium
Complete ground state electronic configuration for the Iridium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d7 6s2
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.
As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.
Atomic Structure of Iridium
Iridium atomic radius is 180 pm, while it's covalent radius is 137 pm.
| Atomic Radius Calculated | 180 pm(1.8 Å) |
| Atomic Radius Empirical | 135 pm (1.35 Å) |
| Atomic Volume | 8.5203 cm3/mol |
| Covalent Radius | 137 pm (1.37 Å) |
| Van der Waals Radius | - |
| Neutron Cross Section | 425 |
| Neutron Mass Absorption | 0.08 |
Spectral Lines of Iridium - Atomic Spectrum of Iridium
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules.
Spectral lines are the result of interaction between a quantum system and a single photon. A spectral line may be observed either as an emission line or an absorption line.
Spectral lines are highly atom-specific, and can be used to identify the chemical composition of any medium. Several elements, including helium, thallium, and caesium, were discovered by spectroscopic means. They are widely used to determine the physical conditions of stars and other celestial bodies that cannot be analyzed by other means.
Emission spectrum of Iridium
Absorption spectrum of Iridium
Iridium Chemical Properties: Iridium Ionization Energies and electron affinity
The electron affinity of Iridium is 151 kJ/mol.
| Valence | 6 |
| Electronegativity | 2.2 |
| ElectronAffinity | 151 kJ/mol |
Ionization Energy of Iridium
Ionization energy is the amount of energy required to remove an electron from an atom or molecule.in chemistry, this energy is expresed in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).
Refer to table below for Ionization energies of Iridium
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1st | 880 |
| 2nd | 1600 |
Iridium Physical Properties
Refer to below table for Iridium Physical Properties
| Density | 22.56 g/cm3(when liquid at m.p density is $19 g/cm3) |
| Molar Volume | 8.5203 cm3/mol |
Elastic Properties
| Young Modulus | 528 |
| Shear Modulus | 210 GPa |
| Bulk Modulus | 320 GPa |
| Poisson Ratio | 0.26 |
Hardness of Iridium - Tests to Measure of Hardness of Element
| Mohs Hardness | 6.5 MPa |
| Vickers Hardness | 1760 MPa |
| Brinell Hardness | 1670 MPa |
Iridium Electrical Properties
Electrical resistivity measures element's electrical resistance or how strongly it resists electric current.The SI unit of electrical resistivity is the ohm-metre (Ω⋅m). While Electrical conductivity is the reciprocal of electrical resistivity. It represents a element's ability to conduct electric current. The SI unit of electrical conductivity is siemens per metre (S/m).
Iridium is a conductor of electricity. Refer to table below for the Electrical properties of Iridium
| Electrical conductors | Conductor |
| Electrical Conductivity | 21000000 S/m |
| Resistivity | 4.7e-8 m Ω |
| Superconducting Point | 0.11 |
Iridium Heat and Conduction Properties
| Thermal Conductivity | 150 W/(m K) |
| Thermal Expansion | 0.0000064 /K |
Iridium Magnetic Properties
| Magnetic Type | Paramagnetic |
| Curie Point | - |
| Mass Magnetic Susceptibility | 1.67e-9 m3/kg |
| Molar Magnetic Susceptibility | 3.21e-10 m3/mol |
| Volume Magnetic Susceptibility | 0.0000377 |
Optical Properties of Iridium
| Refractive Index | - |
Acoustic Properties of Iridium
| Speed of Sound | 4825 m/s |
Iridium Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Iridium
| Melting Point | 2739 K(2465.85 °C, 4470.530 °F) |
| Boiling Point | 4701 K(4427.85 °C, 8002.130 °F) |
| Critical Temperature | - |
| Superconducting Point | 0.11 |
Enthalpies of Iridium
| Heat of Fusion | 26 kJ/mol |
| Heat of Vaporization | 560 kJ/mol |
| Heat of Combustion | - |
Iridium Isotopes - Nuclear Properties of Iridium
Iridium has 36 isotopes, with between 164 and 199 nucleons. Iridium has 2 stable naturally occuring isotopes.
Isotopes of Iridium - Naturally occurring stable Isotopes: 191Ir, 193Ir.
| Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|---|---|
| 164Ir | 77 | 87 | 164 | Synthetic | ||
| 165Ir | 77 | 88 | 165 | Synthetic | ||
| 166Ir | 77 | 89 | 166 | Synthetic | ||
| 167Ir | 77 | 90 | 167 | Synthetic | ||
| 168Ir | 77 | 91 | 168 | Synthetic | ||
| 169Ir | 77 | 92 | 169 | Synthetic | ||
| 170Ir | 77 | 93 | 170 | Synthetic | ||
| 171Ir | 77 | 94 | 171 | Synthetic | ||
| 172Ir | 77 | 95 | 172 | Synthetic | ||
| 173Ir | 77 | 96 | 173 | Synthetic | ||
| 174Ir | 77 | 97 | 174 | Synthetic | ||
| 175Ir | 77 | 98 | 175 | Synthetic | ||
| 176Ir | 77 | 99 | 176 | Synthetic | ||
| 177Ir | 77 | 100 | 177 | Synthetic | ||
| 178Ir | 77 | 101 | 178 | Synthetic | ||
| 179Ir | 77 | 102 | 179 | Synthetic | ||
| 180Ir | 77 | 103 | 180 | Synthetic | ||
| 181Ir | 77 | 104 | 181 | Synthetic | ||
| 182Ir | 77 | 105 | 182 | Synthetic | ||
| 183Ir | 77 | 106 | 183 | Synthetic | ||
| 184Ir | 77 | 107 | 184 | Synthetic | ||
| 185Ir | 77 | 108 | 185 | Synthetic | ||
| 186Ir | 77 | 109 | 186 | Synthetic | ||
| 187Ir | 77 | 110 | 187 | Synthetic | ||
| 188Ir | 77 | 111 | 188 | Synthetic | ||
| 189Ir | 77 | 112 | 189 | Synthetic | ||
| 190Ir | 77 | 113 | 190 | Synthetic | ||
| 191Ir | 77 | 114 | 191 | 37.3% | Stable | N/A |
| 192Ir | 77 | 115 | 192 | Synthetic | Stable | |
| 193Ir | 77 | 116 | 193 | 62.7% | Stable | N/A |
| 194Ir | 77 | 117 | 194 | Synthetic | ||
| 195Ir | 77 | 118 | 195 | Synthetic | ||
| 196Ir | 77 | 119 | 196 | Synthetic | ||
| 197Ir | 77 | 120 | 197 | Synthetic | ||
| 198Ir | 77 | 121 | 198 | Synthetic | ||
| 199Ir | 77 | 122 | 199 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
The United States Department of Transportation (DOT) identifies hazard class of all dangerous elements/goods/commodities either by its class (or division) number or name. The DOT has divided these materials into nine different categories, known as Hazard Classes.
| DOT Numbers | 3089 |
| DOT Hazard Class | 4.1 |
NFPA 704 is a Standard System for the Identification of the Hazards of Materials for Emergency Response. NFPA is a standard maintained by the US based National Fire Protection Association.
The health (blue), flammability (red), and reactivity (yellow) rating all use a numbering scale ranging from 0 to 4. A value of zero means that the element poses no hazard; a rating of four indicates extreme danger.
| NFPA Fire Rating | N/A | N/A |
| NFPA Health Rating | N/A | N/A |
| NFPA Reactivity Rating | N/A | N/A |
| NFPA Hazards | N/A |
| Autoignition Point | - |
| Flashpoint | - |
Database Search
List of unique identifiers to search the element in various chemical registry databases
| Database | Identifier number |
|---|---|
| CAS Number - Chemical Abstracts Service (CAS) | CAS7439-88-5 |
| RTECS Number | - |
| CID Number | CID23924 |
| Gmelin Number | - |
| NSC Number | - |
Compare Iridium with other elements
Compare Iridium with Group 9, Period 6 and Transition Metal elements of the periodic table.
Compare Iridium with all Group 9 elements
Compare Iridium with all Period 6 elements
Compare Iridium with all Transition Metal elements
Frequently Asked Questions (FAQ)
Find the answers to the most frequently asked questions about Iridium