Meitnerium
Meitnerium is a chemical element with symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature that can be created in a laboratory). The most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds.
At a glance
- Atomic number
- 109
- Atomic mass
- 278 u
- Phase
- Solid
- Density
- 37.4 g/cm³
- Melting point
- Unavailable
- Boiling point
- Unavailable
- First ionization energy
- Unavailable
- Electronegativity
- Unavailable
- Electron affinity
- Unavailable
- Molar heat capacity
- Unavailable
- Period
- 7
- Appearance
- Unavailable
Conditions and isotopes affect measured properties. Some properties of short-lived elements are predicted. Electronegativity uses the Pauling scale.
Predicted configuration. These hydrogen-like orbitals omit strong relativistic effects for Meitnerium. Every orbital of each visible subshell is shown: in Shapes as the surface holding half its probability, with light and dark shades for opposite signs of the wavefunction; in Cloud as dots where its electrons are likely to be. Sizes are stepped by shell, like the Shell model.
86 is the [Rn] core total across six shells.
Preparing the orbital view…
109 protons169 neutrons
Meitnerium-278: its most common form in nature, or its longest-lived if it has none. The nucleus is drawn far too big: it’s about 100,000 times smaller than the atom.
The island of stability
Every element heavier than lead is radioactive, and the heavier they get, the faster they fall apart. Meitnerium’s longest-lived known form, Meitnerium-278, has a half-life of 4.5 seconds. Yet physicists predict that a little further on there is an “island” of heavier nuclei that should last much longer.
Meitnerium-278 half-life 4.5 seconds
From uranium, which has lasted since before the Earth formed, lifetimes plunge. But from rutherfordium (104) on, the fall flattens out to seconds and minutes. Those longest-lived forms are also the most neutron-rich ones made so far: more neutrons help, just as the island idea predicts.
Walk towards the islandEach square is one nuclide: a particular number of protons (which element it is) and neutrons. Darker squares last longer. Squares with a dashed outline were measured from only a few atoms, so their half-lives are very uncertain. Tap a square, or use the buttons, to see it.
- Under 1 ms
- 1 ms – 1 s
- 1 s – 1 min
- 1 min – 1 h
- 1 h – 1 day
- Over a day
- Very uncertain
Meitnerium-278
109 protons and 169 neutrons. Half-life 4.5 seconds; it gives off an alpha particle. That’s 15 neutrons short of the island’s predicted centre at 184.
Along each row, adding neutrons mostly makes the nucleus last longer. But no one has made a superheavy nucleus with more than 177 neutrons: they are made by fusing two lighter nuclei, and lighter nuclei don’t have enough neutrons to spare.
Why an island?
- Magic numbers
Protons and neutrons fill shells in the nucleus, much as electrons fill shells around it. Full shells are extra stable: lead-208, with 82 protons and 126 neutrons, is doubly “magic” and never decays.
- The next full shells
Theory predicts the next magic numbers at about 114 protons and 184 neutrons. Estimates of how long nuclei there would last range from minutes to far longer; no one knows.
- Made an atom at a time
Superheavy elements are made by firing a beam of one element at a target of another for weeks. Only a handful of atoms of the heaviest, like oganesson, have ever been seen.
Half-lives and decay modes from the IAEA Live Chart of Nuclides (ENSDF). An element’s longest-lived form counts only half-lives measured to better than their own size; values from only a few atoms are shown on the map with a dashed outline. The island’s outline is a sketch of where theory puts it, not a measurement.
Keep exploring
Explore the stories, imagery, and reference data in more depth. Properties with no value in the reference are marked unavailable.
- MeitneriumRoyal Society of Chemistry
- MeitneriumWikipedia
- Quantum numbers and electron configurationsPurdue
- Hydrogenic wavefunctionsNIST