Electron Configuration of Roentgenium (Rg)
Roentgenium (Rg, Z = 111) has the electron configuration [Rn] 5f¹⁴ 6d¹⁰ 7s¹, filling 7 shells with 2, 8, 18, 32, 32, 18, 1 electrons.
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Roentgenium: every subshell, one by one
Read the configuration like a receipt: each line is one subshell, and the running total climbs exactly to 111 electrons — never one more, never one less.
| Subshell | Electrons | Total so far |
|---|---|---|
| [Rn] | 0 | 86 |
| 5f | 14 | 100 |
| 6d | 10 | 110 |
| 7s | 1 | 111 |
Electrons per shell (K, L, M…)
Grouped by principal quantum number instead of subshell, Roentgenium carries 2 in shell 1, 8 in shell 2, 18 in shell 3, 32 in shell 4, 32 in shell 5, 18 in shell 6, 1 in shell 7. The outermost shell holds 1 electron — the ones that do all the bonding.
How to derive it yourself
Follow the aufbau order (1s → 2s → 2p → 3s → 3p → 4s → 3d → …), pouring 111 electrons into orbitals of capacity 2 (s), 6 (p), 10 (d) and 14 (f) until none remain. Write the filled inner shells as the nearest noble-gas core — for Roentgenium that gives [Rn] 5f¹⁴ 6d¹⁰ 7s¹.
Note: Roentgenium is one of the textbook exceptions to strict aufbau filling — a half-filled or fully-filled d subshell buys extra stability, so its ground-state configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s¹.
Students also ask
How many electron shells does Roentgenium have?
Roentgenium is in period 7, so its electrons occupy 7 shells, holding 2, 8, 18, 32, 32, 18, 1 electrons respectively.
How many valence electrons does Roentgenium have?
Its outermost shell holds 1 electron, so Roentgenium has 1 valence electron that take part in bonding.
What is the noble-gas shorthand for Roentgenium?
The shorthand form is exactly [Rn] 5f¹⁴ 6d¹⁰ 7s¹.