---
title: "Roentgenium (Rg) — element 111"
description: "Roentgenium is element 111, symbol Rg, most stable isotope 282. Configuration, properties, uses and neighbours."
url: https://atoneplace.net/element/roentgenium/
site: "At One Place"
---

# Roentgenium (Rg)

**Roentgenium — element 111: Rg**

[282] · Transition metal · period 7, group 11

Roentgenium sits below gold, and calculations suggest relativistic effects would push it further in the same direction — a stable −1 oxidation state, like the auride ion, and possibly a metal that is not yellow but silvery or reddish. It was named for Wilhelm Röntgen, who discovered X-rays; the naming was proposed in 2004, close to the hundredth anniversary. Three atoms were seen in the original 1994 experiment, and the total ever made is still measured in dozens.

## Properties

- **Atomic number:** 111
- **Symbol:** Rg
- **Mass number of most stable isotope:** [282]
- **Category:** Transition metal
- **Group:** 11
- **Period:** 7
- **Block:** d-block
- **Electron configuration:** [Rn] 7s² 5f¹⁴ 6d⁹
- **Electrons per shell:** 2, 8, 18, 32, 32, 17, 2
- **Oxidation states:** +5, +3, +1, -1
- **Discovered:** 1994 by Sigurd Hofmann and colleagues at GSI Darmstadt

## Electron configuration

- **Full:** 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d⁹
- **Noble gas shorthand:** [Rn] 7s² 5f¹⁴ 6d⁹
- **Shells:** K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 17 · Q: 2

## What it is used for

- Research only; no application outside the laboratory

## Hazards

- Intensely radioactive; exists only as individual atoms in an accelerator

> Melting point, boiling point, density and electronegativity are omitted. The electron configuration is calculated, not observed, and some calculations favour 6d¹⁰ 7s¹. The mass given is the mass number of roentgenium-282, the longest-lived at roughly 100 seconds.

> Several physical properties are not listed for roentgenium because no bulk sample has ever existed. Only a handful of atoms have been produced, often with half-lives measured in seconds, so published melting points and densities for elements in this range are calculations rather than measurements. They are omitted rather than presented as observed values.

## Neighbours in the table

| Z | Element | Symbol | Mass |
| --- | --- | --- | --- |
| 109 | Meitnerium | Mt | [278] |
| 110 | Darmstadtium | Ds | [281] |
| 111 | Roentgenium ← | Rg | [282] |
| 112 | Copernicium | Cn | [285] |
| 113 | Nihonium | Nh | [286] |

## Group 11

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Roentgenium sits in group 11 with copper, silver, gold.

## Common questions

### What is the atomic number of roentgenium?

111. That is the number of protons in its nucleus, which is what defines the element.

### What is the symbol for roentgenium?

Rg.

### What is the electron configuration of roentgenium?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d⁹, or [Rn] 7s² 5f¹⁴ 6d⁹ in noble-gas shorthand.

## Related pages

- [Meitnerium (Mt)](https://atoneplace.net/element/meitnerium/)
- [Darmstadtium (Ds)](https://atoneplace.net/element/darmstadtium/)
- [Copernicium (Cn)](https://atoneplace.net/element/copernicium/)
- [Nihonium (Nh)](https://atoneplace.net/element/nihonium/)
- [Copper (Cu)](https://atoneplace.net/element/copper/)
- [Silver (Ag)](https://atoneplace.net/element/silver/)
- [Gold (Au)](https://atoneplace.net/element/gold/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)