Transition metalElement 105 · d-block

Dubnium (Db)

Dubnium (Db) is a transition metal with atomic number 105; its most stable known isotope has mass number 268. Only a few atoms have ever been made, so its bulk properties are predictions.

105DbDubnium[268]

Atomic number

105

protons

Atomic weight

[268]

most stable isotope

Melting point

—

Boiling point

—

Density

29.3 g/cm³

predicted

Electronegativity

—

Pauling scale

State at 25 °C

Unknown

predicted solid

Discovered

1968–1970

USSR / United States

Dubnium at a glance

Identity

Symbol	Db
Atomic number (Z)	105
Atomic weight	[268] mass number of the most stable isotope
Category	Transition metal
Group	5
Period	7
Block	d-block
CAS number	53850-35-4

Atomic properties

Electron configuration	[Rn] 5f¹⁴ 6d³ 7s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d³ 7s²
Electrons per shell	2, 8, 18, 32, 32, 11, 2
First ionisation energy	6.8 eV (656.1 kJ/mol) 2nd: 14 eV · 3rd: 23.1 eV
Covalent radius	149 pm

Physical properties

State at 25 °C	Unknown (predicted solid)
Density	29.3 g/cm³ (predicted)

Isotopes & abundance

Natural occurrence	Synthetic
Radioactive	Yes
Most stable isotope	²⁶⁸Db — half-life 29 h
Known isotopes	16

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

Dubnium electron configuration

Dubnium has 105 electrons. Written in short form, its ground-state configuration is [Rn] 5f¹⁴ 6d³ 7s² — the electrons of the noble gas radon, plus 5f¹⁴ 6d³ 7s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d³ 7s².

5f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d↑↑↑

7s↑↓

Discovery and name

Discovered

1968–1970 — Joint Institute for Nuclear Research (Dubna) and Lawrence Berkeley Laboratory · USSR / United States.

Name

Dubna, Russia, home of the Joint Institute for Nuclear Research.

Known for

Made one atom at a time; studies show it behaves broadly like niobium and tantalum.

Isotopes of dubnium

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

Isotope	Protons	Neutrons	Half-life
²⁶⁸Db	105	163	29 h

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

Dubnium compared with group 5

The other elements in group 5, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Vanadium	23	50.942	1,910 °C	3,407 °C	6 g/cm³	1.63
Niobium	41	92.906	2,477 °C	4,741 °C	8.57 g/cm³	1.6
Tantalum	73	180.95	3,017 °C	5,455 °C	16.4 g/cm³	1.5
Dubnium	105	[268]	—	—	29.3 g/cm³ (pred.)	—

Frequently asked questions

5 answers

What is the atomic mass of dubnium?

Dubnium has no stable isotopes, so it has no standard atomic weight. Periodic tables show [268], the mass number of its most stable known isotope.

How many protons, neutrons and electrons does dubnium have?

A neutral dubnium atom has 105 protons and 105 electrons. Its most stable isotope, dubnium-268, has 163 neutrons.

What is the electron configuration of dubnium?

[Rn] 5f¹⁴ 6d³ 7s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d³ 7s²).

Is dubnium a metal?

Dubnium is a metal. It is in group 5, period 7.

Who discovered dubnium?

1968–1970 — Joint Institute for Nuclear Research (Dubna) and Lawrence Berkeley Laboratory (USSR / United States).