Meitnerium

01 / A closer look

Meet Meitnerium

Meitnerium has atomic number 109: every atom of this element contains 109 protons. It belongs to period 7, group 9 of the periodic table.

In a neutral atom, the number of electrons equals the number of protons. Isotopes of this element share the same atomic number but have different neutron counts.

02 / Physical properties

Melting point

Not listed

Boiling point

Not listed

Density

Not listed

Isotope mass number

[277]

Melting points, boiling points and densities follow RSC fact boxes. Density is referenced to room temperature; consult the source for pressure and allotrope details. These are reference values, not a claim that every value was experimentally measured. Atomic weights follow CIAAW.

Physical-property source: Royal Society of Chemistry ↗ · Reviewed 24 September 2026

Standard atomic weights follow CIAAW 2024 (abridged). Brackets show an isotope mass number from IUPAC 2022, not a standard atomic weight.

03 / Atomic structure

Atomic structure

Electron configuration

[Rn]7s2 5f14 6d7 (calculated)

Oxidation states

9, 8, 6, 4, 3, 1

Electronegativity · Pauling

Not listed

First ionisation energy

Not listed

Atomic radius

Not listed

04 / Where it is found

Where it is found

Synthesised in particle-accelerator experiments.

Production and export figures depend on the commodity and reporting year. No comparable country quantities have been included for this element in this edition.