ElementsWhat is meitnerium?
Meitnerium is a radioactive element made in particle accelerators. Its properties are mostly predicted, not measured.
What is meitnerium used for?
Research only.
Where the name comes from
In honour of the physicist Lise Meitner.
Key facts
- Symbol
- Mt
- Atomic number
- 109
- Atomic mass
- 277.154 u
- Family
- Transition metal
- Period
- 7
- Group
- 9
- Block
- d
- State at room temperature
- Solid
- Melting point
- not measured
- Boiling point
- not measured
- Density
- not measured
- Electrons per shell
- 2, 8, 18, 32, 32, 15, 2
- Electron configuration
- [Rn]7s2 5f14 6d7
- Common oxidation states
- 9, 8, 6, 4, 3, 1
- Electronegativity (Pauling)
- no value
- First ionisation energy
- not measured
- Electron affinity
- no value
- Atomic radius (van der Waals)
- no value
- Discovered
- 1982
Place in the periodic table
Meitnerium is element number 109. It sits in period 7 (row 7) of the periodic table, in group 9 (column 9), and belongs to the d-block. Just before it comes hassium (108), and just after it comes darmstadtium (110). In the same column, iridium is above it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
At room temperature meitnerium is a solid.
Inside the atom
An atom of meitnerium has 109 protons in its nucleus and, when neutral, 109 electrons around it. The electrons are arranged in 7 shells: 2, 8, 18, 32, 32, 15, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Rn]7s2 5f14 6d7 (predicted).
One mole of meitnerium weighs 277.154 grams, so a single gram contains about 2.17 × 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 meitnerium 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.