Notation. Nuclides are written with the mass number as a left superscript (e.g., ²⁸²Rg).
Columns. Stable? — Roentgenium has no stable isotopes. Half-lives = evaluated values. Decay → daughter(s) shows main branches. Radiation: α, SF (spontaneous fission). Origin: all isotopes are synthetic. Uses: R research only.
Primary data spine: evaluated Isotopes of roentgenium (ENSDF/NUBASE 2020).
Table — ground states
| Nuclide | Z | A | Stable? | Half-life | Decay → daughter(s) | Radiation | Origin | Notes & Uses |
|---|---|---|---|---|---|---|---|---|
| ²⁷²Rg | 111 | 272 | No | ~1.5 ms | α → ²⁶⁸Mt | α | Fusion-evap. | R. |
| ²⁷³Rg | 111 | 273 | No | 5 ms | α → ²⁶⁹Mt | α | Synthetic | R. |
| ²⁷⁴Rg | 111 | 274 | No | 6 ms | α → ²⁷⁰Mt | α | Synthetic | R. |
| ²⁷⁵Rg | 111 | 275 | No | 10 ms | α → ²⁷¹Mt | α | Synthetic | R. |
| ²⁷⁶Rg | 111 | 276 | No | 1.0 s | α → ²⁷²Mt | α | Synthetic | R. |
| ²⁷⁷Rg | 111 | 277 | No | 1.0 ms | SF (dominant) | SF | Synthetic | R. |
| ²⁷⁸Rg | 111 | 278 | No | 4.0 ms | α → ²⁷⁴Mt | α | Synthetic | R. |
| ²⁷⁹Rg | 111 | 279 | No | 170 ms | α → ²⁷⁵Mt | α | Synthetic | R. |
| ²⁸⁰Rg | 111 | 280 | No | 3.6 s | α → ²⁷⁶Mt | α | Synthetic | R. |
| ²⁸¹Rg | 111 | 281 | No | 26 s | α → ²⁷⁷Mt; SF | α; SF | Synthetic (cold fusion, GSI) | Longest-lived isotope; key for chemistry experiments. |
| ²⁸²Rg | 111 | 282 | No | 2.1 min | α → ²⁷⁸Mt | α | Synthetic | Among the most useful for studies. |
| ²⁸³Rg | 111 | 283 | No | 5.1 min | α → ²⁷⁹Mt; SF minor | α; SF | Synthetic | Longest-lived confirmed isotope. |
| ²⁸⁴Rg | 111 | 284 | No | 38 s | α → ²⁸⁰Mt | α | Synthetic | R. |
Natural isotopes of roentgenium
- None.
- All isotopes are synthetic, first produced in 1994 at GSI Darmstadt by fusing nickel-64 with bismuth-209.
Applied & research highlights
- ²⁸³Rg (5 min): the most stable isotope; enabled first chemical experiments with roentgenium.
- ²⁸¹Rg and ²⁸²Rg also long-lived enough to permit gas-phase chromatography studies, testing whether Rg behaves like Group 11 metals (copper, silver, gold).
- Experimental results suggest Rg is noble-metal-like, but with relativistic effects modifying its chemistry.
- No applications outside fundamental research — produced in atom-scale amounts.
Totals — Roentgenium (Z = 111)
- Ground-state isotopes listed13 (A = 272–284).
- Stable0.
- Unstable13.
Running cumulative totals (through Rg):
From Ds ledger: ≥ 3 289 total, 252 stable, ≥ 3 036 unstable.
Add Rg (+13 total, +0 stable, +13 unstable) → ≥ 3 302 total, 252 stable, ≥ 3 049 unstable.
Sources
- Isotopic list (A = 272–284)Isotopes of roentgenium (ENSDF/NUBASE 2020).
- Discovery (1994, GSI Darmstadt)fusion of Bi-209 + Ni-64.
- Chemistry experiments (²⁸¹Rg, ²⁸³Rg)transactinide studies confirming Group 11 behavior.
Next element: Copernicium — Cn (Z = 112).
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