Iridium (symbol Ir, atomic number 77) is the most corrosion-resistant metal and the marker of the dinosaur-killing asteroid. It is classified as a transition metal and sits in group 9, period 6 of the periodic table.
Overview
Iridium is the chemical element with atomic number 77 and the symbol Ir. With a standard atomic weight of 192.22, it is a transition metal. In the periodic table it occupies group 9 and period 6, and under standard conditions it is normally a solid. Iridium is the most corrosion-resistant metal and the marker of the dinosaur-killing asteroid.
Atomic structure
An atom of Iridium has 77 protons in its nucleus and, when neutral, 77 electrons arranged in the configuration [Xe] 4f14 5d7 6s2. Its standard atomic weight of 192.22 reflects the natural mix of its stable isotopes.
Discovery and place in the table
Iridium was discovered in 1803 by Smithson Tennant. It follows Osmium (Os) and precedes Platinum (Pt) in order of atomic number.
| Atomic number | 77 |
|---|---|
| Symbol | Ir |
| Atomic mass | 192.22 |
| Category | Transition metal |
| Group | 9 |
| Period | 6 |
| Electron configuration | [Xe] 4f14 5d7 6s2 |
| Phase at STP | Solid |
| Discovered | 1803 (Smithson Tennant) |