Meitnerium (Mt)

Meitnerium honours Lise Meitner, who worked out that the uranium nucleus had split when Otto Hahn found barium in his samples and could not explain it — and who was left off the Nobel Prize he received for it. It is the only element named solely for a non-mythological woman; curium honours Marie and Pierre Curie together. The discovery was a single atom, produced at Darmstadt in August 1982 and identified by its decay chain, and only a few dozen atoms have been made since.

Properties

Atomic number

109

Symbol

Mt

Mass number of most stable isotope

[278]

Category

Transition metal

Group

9

Period

7

Block

d-block

Electron configuration

[Rn] 7s² 5f¹⁴ 6d⁷

Electrons per shell

2, 8, 18, 32, 32, 15, 2

Oxidation states

+9, +8, +6, +4, +3, +1

Discovered

1982 by Peter Armbruster, Gottfried Münzenberg 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 6d⁷

Noble gas shorthand

[Rn] 7s² 5f¹⁴ 6d⁷

Shells

K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 15 · 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: no measurement is possible. The electron configuration is calculated, not observed. The mass given is the mass number of meitnerium-278, the longest-lived at a few seconds.

Several physical properties are not listed for meitnerium 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

Group 9

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Meitnerium sits in group 9 with cobalt, rhodium, iridium.