Nihonium (Nh)
Element 113 · Post-transition metal · atomic mass [286] u · group 13, period 7
Electron shells: 2, 8, 18, 32, 32, 18, 3
Nihonium was the first element discovered in Asia, after nine years of experiments that produced three atoms. RIKEN's team had to argue their case for years.
RIKEN ran their experiment for nine years to produce three atoms of nihonium.
- Atomic number
- 113
- Atomic mass
- [286] u
- Electron configuration
- [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹
- Group · period · block
- 13 · 7 · p
- Oxidation states
- —
- Electronegativity
- Not measured
- Melting point
- —
- Boiling point
- —
- Density
- Not measured
- State at 20 °C
- Unknown
- Appearance
- Unknown; presumed metallic
- Discovered
- RIKEN, Japan, 2004
113 protons, and 113 electrons when neutral
Mass number of the longest-lived isotope — no standard atomic weight exists
Predicted, not measured
Boron group
What Nihonium is used for
- Scientific research only
Atomic structure of Nihonium
A neutral nihonium atom has 113 protons and 113 electrons. Its most common isotope carries about 173 neutrons, which is where the mass number 286 comes from. Change the neutron count and you have a different isotope of nihonium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 32, 18, 3. In orbital notation that is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹, leaving 3 valence electrons in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Nihonium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Nihonium sits in the periodic table
Metals to the right of the d-block. Softer, lower-melting and more brittle than the transition metals, with more covalent character in their bonding.
- Directly above: Thallium — same group, so similar chemistry with a smaller atom.
- One proton lighter: Copernicium.
- One proton heavier: Flerovium.
Discovery and naming
Nihonium was discovered by RIKEN, Japan in 2004. Its name comes from Nihon, a Japanese name for Japan, which is also why its symbol (Nh) does not match its English name.
Every isotope of nihonium is radioactive, so it has no standard atomic weight. Periodic tables show the mass number of its longest-lived isotope in square brackets instead.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Nihonium?
Nihonium has no stable isotope, so it has no standard atomic weight. Periodic tables instead show 286 in square brackets — the mass number of its longest-lived isotope.
How many protons, neutrons and electrons does Nihonium have?
Nihonium has 113 protons, because the atomic number is the proton count and that is what makes an atom Nihonium at all. A neutral Nihonium atom has the same number of electrons, 113. The neutron count varies by isotope; the most common one has about 173, since 286 − 113 = 173.
What is the electron configuration of Nihonium?
The electron configuration of Nihonium is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹, though for an element this heavy the configuration is predicted from theory rather than measured. Its electrons are arranged 2, 8, 18, 32, 32, 18, 3 across 7 shells.
Is Nihonium a metal?
Yes. Nihonium is classified as a post-transition metal, on the metallic side of the table.
What group and period is Nihonium in?
Nihonium is in group 13 (the boron group), period 7, in the p-block. The group is its column and the period is its row.
What is Nihonium used for?
Scientific research only. Nihonium was the first element discovered in Asia, after nine years of experiments that produced three atoms.
Who discovered Nihonium, and where does its name come from?
Nihonium (Nh) was discovered by RIKEN, Japan in 2004. The name comes from Nihon, a Japanese name for Japan.
Is Nihonium radioactive?
Yes. Every isotope of Nihonium is radioactive — it has no stable form at all, which is why the periodic table shows its mass in square brackets rather than as a standard atomic weight.