Unknown propertiesElement 113 · p-block

Nihonium (Nh)

Nihonium (Nh), element 113, is a synthetic superheavy element whose chemical properties have not been measured; its most stable known isotope has mass number 286. Only a few atoms have ever been made, so its bulk properties are predictions.

113NhNihonium[286]

Atomic number

113

protons

Atomic weight

[286]

most stable isotope

Melting point

—

Boiling point

—

Density

16 g/cm³

predicted

Electronegativity

—

Pauling scale

State at 25 °C

Unknown

predicted solid

Discovered

2004

Japan (Wakō)

Nihonium at a glance

Identity

Symbol	Nh
Atomic number (Z)	113
Atomic weight	[286] mass number of the most stable isotope
Category	Unknown properties
Group	13 — boron group
Period	7
Block	p-block
CAS number	54084-70-7

Atomic properties

Electron configuration	[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹ Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s² 7p¹
Electrons per shell	2, 8, 18, 32, 32, 18, 3
Covalent radius	136 pm

Physical properties

State at 25 °C	Unknown (predicted solid)
Density	16 g/cm³ (predicted)

Isotopes & abundance

Natural occurrence	Synthetic
Radioactive	Yes
Most stable isotope	²⁸⁶Nh — half-life 12 s
Known isotopes	13

Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.

Nihonium electron configuration

Nihonium has 113 electrons. Written in short form, its ground-state configuration is [Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹ — the electrons of the noble gas radon, plus 5f¹⁴ 6d¹⁰ 7s² 7p¹.Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s² 7p¹.

As a member of group 13 it has 3 valence electrons in its outer shell (shell 7), which largely decide its chemistry.

5f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d↑↓↑↓↑↓↑↓↑↓

7s↑↓

7p↑

Discovery and name

Discovered

2004 — Kosuke Morita and co-workers (RIKEN) · Japan (Wakō).

Name

Nihon, Japanese for Japan.

Known for

The first element discovered in Asia, by RIKEN in Japan.

Isotopes of nihonium

Nihonium has no stable isotopes and does not occur naturally in significant amounts. Its longest-lived known isotope is:

Isotope	Protons	Neutrons	Half-life
²⁸⁶Nh	113	173	12 s

13 isotopes of nihonium are known in our data set (half-lives as published in nuclear data tables).

Nihonium compared with group 13

The other elements in group 13 (boron group), from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Boron	5	10.81	2,077 °C	4,000 °C	2.34 g/cm³	2.04
Aluminum	13	26.982	660 °C	2,519 °C	2.7 g/cm³	1.61
Gallium	31	69.723	30 °C	2,229 °C	5.91 g/cm³	1.81
Indium	49	114.82	157 °C	2,027 °C	7.31 g/cm³	1.78
Thallium	81	204.38	304 °C	1,473 °C	11.8 g/cm³	1.62
Nihonium	113	[286]	—	—	16 g/cm³ (pred.)	—

Frequently asked questions

4 answers

What is the atomic mass of nihonium?

Nihonium has no stable isotopes, so it has no standard atomic weight. Periodic tables show [286], the mass number of its most stable known isotope.

How many protons, neutrons and electrons does nihonium have?

A neutral nihonium atom has 113 protons and 113 electrons. Its most stable isotope, nihonium-286, has 173 neutrons.

What is the electron configuration of nihonium?

[Rn] 5f¹⁴ 6d¹⁰ 7s² 7p¹ (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s² 7p¹).

Who discovered nihonium?

2004 — Kosuke Morita and co-workers (RIKEN) (Japan (Wakō)).