Nihonium (Element 113): Properties, Isotopes and Half-Lives
Last reviewed on 1 October 2026.
Nihonium (Nh, element 113) has six known isotopes, nihonium-278 and nihonium-282 to -286. The longest-lived, nihonium-286, has a half-life of roughly 10 seconds. All of them decay mainly by alpha emission to roentgenium (element 111). Since only single atoms have been made, its bulk properties are predictions. It is expected to be a dense, soft post-transition metal that, like thallium, favours the +1 oxidation state.
Known Isotopes of Nihonium
An isotope's mass number is its protons (always 113 for nihonium) plus its neutrons. The half-lives below are approximate. They come from very few observed atoms, and published values differ between measurements.
| Isotope | Neutrons | Approx. half-life | How it was produced |
|---|---|---|---|
| Nihonium-278 | 165 | about 1–2 milliseconds | Directly, from zinc-70 + bismuth-209 (RIKEN) |
| Nihonium-282 | 169 | under 0.1 second | Directly, from calcium-48 + neptunium-237 (Dubna) |
| Nihonium-283 | 170 | about 0.1 second | Alpha decay of moscovium-287 |
| Nihonium-284 | 171 | about 1 second | Alpha decay of moscovium-288 |
| Nihonium-285 | 172 | a few seconds | Alpha decay of moscovium-289 (from tennessine-293) |
| Nihonium-286 | 173 | roughly 10 seconds | Alpha decay of moscovium-290 (from tennessine-294) |
The pattern is clear: the more neutrons, the longer the isotope lasts. This is one of the observations behind the predicted "island of stability".
How Nihonium Is Made: Cold and Hot Fusion
Nihonium has been produced in two different ways:
- Cold fusion (RIKEN, Japan). Zinc-70 ions, accelerated to about 10% of the speed of light, strike a bismuth-209 target: 70Zn + 209Bi → 278Nh + n. The compound nucleus is formed with relatively little excess energy and needs to emit only one neutron. However, the reaction is extremely rare. RIKEN collected three atoms in about nine years of beam time, in 2004, 2005 and 2012.
- Hot fusion (JINR Dubna with US partners). Calcium-48 beams strike actinide targets. With americium-243 they make moscovium (115), which alpha-decays to nihonium-283 or nihonium-284. With berkelium-249 they make tennessine (117), whose chain passes through nihonium-285 and nihonium-286. With neptunium-237 they make nihonium-282 directly. These isotopes are more neutron-rich, so they last longer than RIKEN's nihonium-278.
Who was credited with the discovery, and why, is covered on our main element 113 (nihonium) discovery and naming page.
Decay Chains: How a Single Atom Is Identified
A nihonium atom is never seen directly. Detectors record the energy and timing of each alpha particle as the atom decays step by step into lighter elements. RIKEN's 2012 atom followed this chain:
278Nh → 274Rg → 270Mt → 266Bh → 262Db → 258Lr → 254Md
Six consecutive alpha decays ended in isotopes of dubnium, lawrencium and mendelevium whose decay signatures were already known. That link to known nuclei is what made the identification convincing. The two earlier RIKEN atoms ended in spontaneous fission of dubnium-262 instead.
Predicted Physical Properties
No visible amount of nihonium has ever existed, so its bulk properties come from calculations and from trends down group 13. Rounded values from published predictions:
| Property | Predicted value |
|---|---|
| State at room temperature | Solid metal |
| Density | about 16 g/cm³ (denser than lead at 11.3 g/cm³) |
| Melting point | about 430 °C (700 K) |
| Boiling point | about 1,150 °C (roughly 1,400 K) |
| Atomic radius | about 170 picometres |
Different theoretical studies give different numbers. Treat these as estimates, not measurements.
Predicted Chemistry
- Oxidation states: +1 is expected to be the most stable, continuing the trend from indium to thallium. +3 should be possible but less favoured.
- Why +1: relativistic effects strongly stabilise the 7s electron pair and the 7p1/2 orbital, so the "inert pair" holds back from bonding.
- Reactivity: nihonium is expected to be less reactive than thallium.
- Experiments so far: single-atom gas-phase chemistry experiments on nihonium have only recently begun. They are very hard because each atom lasts seconds at most, and conclusions remain limited.
| Element | Z | Main oxidation states | Melting point |
|---|---|---|---|
| Boron (B) | 5 | +3 | 2,076 °C |
| Aluminium (Al) | 13 | +3 | 660 °C |
| Gallium (Ga) | 31 | +3 | 29.8 °C |
| Indium (In) | 49 | +3 (also +1) | 156.6 °C |
| Thallium (Tl) | 81 | +1 (also +3) | 304 °C |
| Nihonium (Nh) | 113 | +1, +3 (predicted) | ~430 °C (predicted) |
For nihonium's place in the table and its neighbours, see what element is 113 on the periodic table.
Nihonium and the Island of Stability
Nuclear theory predicts extra stability for nuclei near "magic" numbers of protons and neutrons. For superheavy elements, these are often placed around 114 (or 120/126) protons and 184 neutrons. Nihonium-286 has 173 neutrons, still 11 short of 184. Its half-life of about 10 seconds, compared with milliseconds for nihonium-278, fits the expectation that nuclei grow more stable as they approach that region. Even more neutron-rich nihonium isotopes might live longer, but no one has yet found a way to make them.
Frequently Asked Questions
What is the most stable isotope of nihonium?
The longest-lived known isotope is nihonium-286, with a half-life of roughly 10 seconds. That is why nihonium's atomic weight is written as [286].
How is nihonium made?
Nihonium is made in particle accelerators. RIKEN fused zinc-70 ions with bismuth-209 to make nihonium-278 directly. Dubna fused calcium-48 with neptunium-237 to make nihonium-282, and obtained heavier nihonium isotopes as alpha-decay products of moscovium (element 115).
Is nihonium a solid, liquid or gas?
Nihonium is predicted to be a dense solid metal at room temperature, with a density of about 16 g/cm³ and a melting point around 430 °C. No visible amount has ever been made, so none of this has been measured.
What does nihonium decay into?
Nihonium isotopes decay mainly by emitting an alpha particle, which turns them into roentgenium (element 111). For example, nihonium-278 decays to roentgenium-274, then meitnerium-270, bohrium-266 and dubnium-262.