Iridium (Ir)
Iridium is element 77, a transition metal in group 9, period 6. A neutral atom has 77 protons, 115 neutrons and 77 electrons, 2 of them valence electrons.
Transition metal- Atomic number
- 77
- Atomic mass
- 192.22 u
- Valence electrons
- 2*
- Protons · neutrons
- 77 · 115
- Electrons per shell
- 2, 8, 18, 32, 15, 2
- At room temperature
- solid
Bohr model of iridium
The Bohr model draws iridium as a nucleus of 77 protons and 115 neutrons, with its 77 electrons on 6 circular shells: 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 15 in shell 5, 2 in shell 6. Press Build the atom to watch the shells fill from the inside out. The outer ring (the P shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of iridium
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d⁷
Short form (noble gas notation): [Xe] 6s² 4f¹⁴ 5d⁷. The [Xe] stands for the electrons of xenon, the noble gas before it.
How many valence electrons does iridium have?
Iridium has 2 valence electrons.
Iridium is a transition metal, so its valence electrons are less clear-cut than for main-group elements. It has 2 electrons in its outermost shell (shell 6), and electrons in its inner d subshell can also take part in bonding.
Protons, neutrons and electrons
| Protons | 77 | equal to the atomic number |
|---|---|---|
| Electrons | 77 | equal to the protons in a neutral atom |
| Neutrons | 115 | mass number 192 − 77 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Iridium properties
| Symbol | Ir |
|---|---|
| Category | Transition metal |
| Group · period · block | 9 · 6 · d |
| Atomic mass | 192.22 u |
| State at 25 °C | solid |
| Melting point | 2,719 K (2,450 °C, 4,430 °F) |
| Boiling point | 4,701 K (4,430 °C, 8,000 °F) |
| Density | 22.42 g/cm³ |
| Electronegativity (Pauling) | 2.2 |
| Atomic radius | 202 pm |
| First ionization energy | 9.1 eV |
| Electron affinity | 1.565 eV |
| Oxidation states | +4, +3 |
| Common ion charge | +4, +3 |
| Discovered | 1803 by Smithson Tennant |
Where iridium sits on the periodic table
Group 9: Cobalt, Rhodium, Meitnerium.
Questions about iridium
How many valence electrons does iridium have?
Iridium has 2 valence electrons in its outer shell; inner d or f electrons can also bond.
How many protons, neutrons and electrons does iridium have?
A neutral iridium atom has 77 protons and 77 electrons. Its most common form has about 115 neutrons (mass number 192 − 77 protons).
What is the electron configuration of iridium?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d⁷, written in short form as [Xe] 6s² 4f¹⁴ 5d⁷.
What does the Bohr model of iridium look like?
A nucleus of 77 protons and 115 neutrons, circled by 6 electron shells holding 2, 8, 18, 32, 15, 2 electrons.
What is the atomic number of iridium?
77. The atomic number is the number of protons in the nucleus, and it is what makes an atom iridium.