Transition metalElement 106 · d-block

Seaborgium (Sg)

Seaborgium (Sg) is a transition metal with atomic number 106; its most stable known isotope has mass number 269. Only a few atoms have ever been made, so its bulk properties are predictions.

106SgSeaborgium[269]

Atomic number

106

protons

Atomic weight

[269]

most stable isotope

Melting point

—

Boiling point

—

Density

35 g/cm³

predicted

Electronegativity

—

Pauling scale

State at 25 °C

Unknown

predicted solid

Discovered

1974

United States (Berkeley)

Seaborgium at a glance

Identity

Symbol	Sg
Atomic number (Z)	106
Atomic weight	[269] mass number of the most stable isotope
Category	Transition metal
Group	6
Period	7
Block	d-block
CAS number	54038-81-2

Atomic properties

Electron configuration	[Rn] 5f¹⁴ 6d⁴ 7s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁴ 7s²
Electrons per shell	2, 8, 18, 32, 32, 12, 2
First ionisation energy	7.8 eV (752.6 kJ/mol) 2nd: 17.1 eV · 3rd: 25.8 eV
Covalent radius	143 pm

Physical properties

State at 25 °C	Unknown (predicted solid)
Density	35 g/cm³ (predicted)

Isotopes & abundance

Natural occurrence	Synthetic
Radioactive	Yes
Most stable isotope	²⁶⁹Sg — half-life 5 min
Known isotopes	16

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

Seaborgium electron configuration

Seaborgium has 106 electrons. Written in short form, its ground-state configuration is [Rn] 5f¹⁴ 6d⁴ 7s² — the electrons of the noble gas radon, plus 5f¹⁴ 6d⁴ 7s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁴ 7s².

5f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d↑↑↑↑

7s↑↓

Discovery and name

Discovered

1974 — Albert Ghiorso and co-workers · United States (Berkeley).

Name

Glenn T. Seaborg.

Known for

The first element named after a living person (Glenn Seaborg, in 1997).

Isotopes of seaborgium

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

Isotope	Protons	Neutrons	Half-life
²⁶⁹Sg	106	163	5 min

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

Seaborgium compared with group 6

The other elements in group 6, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Chromium	24	51.996	1,907 °C	2,671 °C	7.15 g/cm³	1.66
Molybdenum	42	95.95	2,622 °C	4,639 °C	10.2 g/cm³	2.16
Tungsten	74	183.84	3,422 °C	5,930 °C	19.3 g/cm³	2.36
Seaborgium	106	[269]	—	—	35 g/cm³ (pred.)	—

Frequently asked questions

5 answers

What is the atomic mass of seaborgium?

Seaborgium 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 seaborgium have?

A neutral seaborgium atom has 106 protons and 106 electrons. Its most stable isotope, seaborgium-269, has 163 neutrons.

What is the electron configuration of seaborgium?

[Rn] 5f¹⁴ 6d⁴ 7s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d⁴ 7s²).

Is seaborgium a metal?

Seaborgium is a metal. It is in group 6, period 7.

Who discovered seaborgium?

1974 — Albert Ghiorso and co-workers (United States (Berkeley)).