ElementsWhat is roentgenium?
Roentgenium is a radioactive element made in particle accelerators. It sits under gold in the table, but too few atoms have been made to see what it looks like.
What is roentgenium used for?
Research only.
Where the name comes from
In honour of Wilhelm Röntgen, who discovered X-rays.
Key facts
- Symbol
- Rg
- Atomic number
- 111
- Atomic mass
- 282.169 u
- Family
- Transition metal
- Period
- 7
- Group
- 11
- Block
- d
- State at room temperature
- Solid (expected)
- Melting point
- not measured
- Boiling point
- not measured
- Density
- not measured
- Electrons per shell
- 2, 8, 18, 32, 32, 17, 2
- Electron configuration
- [Rn]7s2 5f14 6d9
- Common oxidation states
- 5, 3, 1, -1
- Electronegativity (Pauling)
- no value
- First ionisation energy
- not measured
- Electron affinity
- no value
- Atomic radius (van der Waals)
- no value
- Discovered
- 1994
Place in the periodic table
Roentgenium is element number 111. It sits in period 7 (row 7) of the periodic table, in group 11 (column 11), and belongs to the d-block. Just before it comes darmstadtium (110), and just after it comes copernicium (112). In the same column, gold is above it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
Too few atoms of roentgenium have been made to measure its bulk properties. It is expected to be a solid at room temperature.
Inside the atom
An atom of roentgenium has 111 protons in its nucleus and, when neutral, 111 electrons around it. The electrons are arranged in 7 shells: 2, 8, 18, 32, 32, 17, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Rn]7s2 5f14 6d9 (predicted).
One mole of roentgenium weighs 282.169 grams, so a single gram contains about 2.13 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains roentgenium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.