Lutetium has 71 electrons arranged as 2, 8, 18, 32, 9, 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 lutetium that gives [Xe] 4f14 5d1 6s2.
| Atomic number | 71 |
| Symbol | Lu |
| Atomic mass | 174.97 u |
| Group | f-block (no group number) |
| Period | 6 |
| Block | f-block |
| Category | Lanthanide |