Meitnerium is a synthetic, highly radioactive transactinide element in group 9. It does not occur naturally and is produced in particle accelerators in atom-by-atom amounts. Only short-lived isotopes are known.
Meitnerium (Mt) is a synthetic transactinide with atomic number 109. It lies in Group 9 (the cobalt–rhodium–iridium family) and period 7. Because it does not occur in nature, it is created atom-by-atom in particle accelerators.
Mt was first synthesized in 1982 at GSI Darmstadt by bombarding a bismuth target with iron ions. A classic discovery route is:
\(^{209}\mathrm{Bi}(^{58}\mathrm{Fe},\,n)\,^{266}\mathrm{Mt}\)
The hot compound nucleus emits a neutron (\(n\)) to reach a specific Mt isotope, which is then swept to detectors within milliseconds.
Fresh Mt atoms recoil from the target into a physical/chemical separator and are implanted into position-sensitive detectors. Identification relies on time-correlated decay chains (mostly \(\alpha\) decays and sometimes spontaneous fission) with characteristic energies and lifetimes.
\(^{A}_{109}\mathrm{Mt} \xrightarrow{\alpha} \, ^{A-4}_{107}\mathrm{Bh} + \alpha \;\to\; \cdots\)
By analogy with Group-9 congeners, Mt is expected to access +3 and +1 in condensed-phase chemistry, with high-valent oxo/oxyhalide species possible under strongly oxidizing conditions. Gas-phase theory also allows very high formal states (up to +8 or higher in transient molecular ions), though such species have not been established experimentally for Mt.
Single-atom gas-phase studies (by analogy and theory) suggest volatile oxyhalides and halides similar to iridium/rhodium chemistry under appropriate conditions (e.g., MtOxCly species). In aqueous systems, if accessible, Mt(III) complexes with hard donor ligands would be expected, but direct solution chemistry is not yet established.
Relativistic calculations and periodic trends support a ground-state configuration close to [Rn] 5f14 6d7 7s2, paralleling iridium’s d-electron count but with stronger relativistic effects in the 6d orbitals.
Several short-lived isotopes (mass numbers near 266–278) have been reported. Dominant decay modes are alpha decay and spontaneous fission, with half-lives typically from milliseconds to seconds (occasionally longer), depending on the isotope.
Experiments produce only a few atoms that decay quickly, so macroscopic samples cannot be prepared. As a result, properties such as density, crystal structure, melting point, and color are predicted from trends and theory rather than measured directly.
Yes. Mt is a radiotoxic heavy element. Although experiments involve atom-scale quantities, all work is performed with remote handling, rapid separators, shielding, and rigorous radiological controls in specialized facilities.
Production (stylized fusion–evaporation):
\(^{209}\mathrm{Bi}(^{58}\mathrm{Fe},\,n)\,^{266}\mathrm{Mt}\)
Generic decay:
\(^{266}\mathrm{Mt} \;\to\; ^{262}\mathrm{Bh} + \alpha\)