Nihonium

properties predicted

Nihonium (Nh) is a post-transition metal with atomic number 113. It has no stable isotope and no characteristic isotopic composition on Earth, so it has no standard atomic weight. CIAAW lists nihonium-285 and nihonium-286 as its longest-lived isotopes, and the mass number used here is 286. Its electron configuration is predicted to be [Rn] 5f14 6d10 7s2 7p1, which gives it 3 valence electrons.

Nihonium key data

Symbol	Nh
Atomic number	113
Mass number (one of its longest-lived isotopes)	286
Protons	113
Neutrons (nihonium-286)	173
Electrons (neutral atom)	113
Valence electrons	3
Category	Post-transition metal
Period	7
Group	13
Block	p-block
Noble gas notation	[Rn] 5f14 6d10 7s2 7p1
Full electron configuration	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

Mass number: IUPAC CIAAW radioactive elements, from NUBASE2020.

Properties of nihonium

From PubChem, the US National Institutes of Health. Public domain. Most properties of this element are predicted, because only a few atoms have ever been made.

Predicted state at room temperature	Solid
Discovered	2004

Nihonium electron configuration

The full electron configuration of nihonium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d10 7s2 7p1. With the noble-gas core collapsed it is [Rn] 5f14 6d10 7s2 7p1, and the outermost subshell is 7p1.

Bohr model of nihonium (Nh): a nucleus and seven shells holding 2, 8, 18, 32, 32, 18 and 3 electrons from the inside out. — Bohr model of nihonium (Nh). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Orbital box diagram of nihonium (Nh), [Rn] 5f14 6d10 7s2 7p1, with the radon core drawn as one bar: one box per orbital, filled by Hund’s rule, showing one unpaired electron, in 7p. — Orbital diagram of nihonium (Nh). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one nihonium atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

one atom = 286 / (6.02214076 × 10²³)
= 4.7491 × 10⁻²² g

Atoms in one gram

atoms per gram = 6.02214076 × 10²³ / 286
= 2.1056 × 10²¹ atoms

Nihonium has no standard atomic weight, because it has neither a stable isotope nor a characteristic isotopic composition on Earth. The figure used above is the mass number of nihonium-286, so treat these as nominal.

Nihonium on the periodic table

Nihonium is in period 7, group 13, in the p-block.

The other elements of group 13 are boron, aluminium, gallium, indium and thallium.