Iridium has 77 electrons arranged as 2, 8, 18, 32, 15, 2 across 6 shells, which is why it sits in period 6.
Start from the previous noble gas core, written in square brackets, then add the remaining electrons in filling order. For iridium that gives [Xe] 4f14 5d7 6s2.
| Atomic number | 77 |
| Symbol | Ir |
| Atomic mass | 192.22 u |
| Group | 9 |
| Period | 6 |
| Block | d-block |
| Category | Transition metal |
| Element | Configuration |
|---|---|
| Cobalt | [Ar] 3d7 4s2 |
| Rhodium | [Kr] 4d8 5s1 |
| Meitnerium | [Rn] 5f14 6d7 7s2 |