Cadmium has 48 electrons arranged as 2, 8, 18, 18, 2 across 5 shells, which is why it sits in period 5.
Start from the previous noble gas core, written in square brackets, then add the remaining electrons in filling order. For cadmium that gives [Kr] 4d10 5s2.
| Atomic number | 48 |
| Symbol | Cd |
| Atomic mass | 112.41 u |
| Group | 12 |
| Period | 5 |
| Block | d-block |
| Category | Transition metal |
| Element | Configuration |
|---|---|
| Zinc | [Ar] 3d10 4s2 |
| Mercury | [Xe] 4f14 5d10 6s2 |
| Copernicium | [Rn] 5f14 6d10 7s2 |