Transition metalElement 108 · d-block

Hassium (Hs)

Hassium (Hs) is a transition metal with atomic number 108; its most stable known isotope has mass number 269. Only a few atoms have ever been made, so its bulk properties are predictions.

108HsHassium[269]

Atomic number

108

protons

Atomic weight

[269]

most stable isotope

Melting point

—

Boiling point

—

Density

40.7 g/cm³

predicted

Electronegativity

—

Pauling scale

State at 25 °C

Unknown

predicted solid

Discovered

1984

Germany (Darmstadt)

Hassium at a glance

Identity

Symbol	Hs
Atomic number (Z)	108
Atomic weight	[269] mass number of the most stable isotope
Category	Transition metal
Group	8
Period	7
Block	d-block
CAS number	54037-57-9

Atomic properties

Electron configuration	[Rn] 5f¹⁴ 6d⁶ 7s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁶ 7s²
Electrons per shell	2, 8, 18, 32, 32, 14, 2
First ionisation energy	7.6 eV (733.3 kJ/mol) 2nd: 18.2 eV · 3rd: 29.3 eV
Covalent radius	134 pm

Physical properties

State at 25 °C	Unknown (predicted solid)
Density	40.7 g/cm³ (predicted)

Isotopes & abundance

Natural occurrence	Synthetic
Radioactive	Yes
Most stable isotope	²⁶⁹Hs — half-life 15 s
Known isotopes	18

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

Hassium electron configuration

Hassium has 108 electrons. Written in short form, its ground-state configuration is [Rn] 5f¹⁴ 6d⁶ 7s² — the electrons of the noble gas radon, plus 5f¹⁴ 6d⁶ 7s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁶ 7s².

5f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d↑↓↑↑↑↑

7s↑↓

Discovery and name

Discovered

1984 — Peter Armbruster and Gottfried Münzenberg (GSI) · Germany (Darmstadt).

Name

Latin Hassia, the German state of Hesse.

Known for

Forms a volatile tetroxide like osmium, confirming its place in group 8.

Isotopes of hassium

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

Isotope	Protons	Neutrons	Half-life
²⁶⁹Hs	108	161	15 s

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

Hassium compared with group 8

The other elements in group 8, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Iron	26	55.845	1,538 °C	2,861 °C	7.87 g/cm³	1.83
Ruthenium	44	101.07	2,333 °C	4,147 °C	12.1 g/cm³	2.2
Osmium	76	190.23	3,033 °C	5,008 °C	22.587 g/cm³	2.2
Hassium	108	[269]	—	—	40.7 g/cm³ (pred.)	—

Frequently asked questions

5 answers

What is the atomic mass of hassium?

Hassium has no stable isotopes, so it has no standard atomic weight. Periodic tables show [269], the mass number of its most stable known isotope.

How many protons, neutrons and electrons does hassium have?

A neutral hassium atom has 108 protons and 108 electrons. Its most stable isotope, hassium-269, has 161 neutrons.

What is the electron configuration of hassium?

[Rn] 5f¹⁴ 6d⁶ 7s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁶ 7s²).

Is hassium a metal?

Hassium is a metal. It is in group 8, period 7.

Who discovered hassium?

1984 — Peter Armbruster and Gottfried Münzenberg (GSI) (Germany (Darmstadt)).