Transition metalElement 104 · d-block

Rutherfordium (Rf)

Rutherfordium (Rf) is a transition metal with atomic number 104; its most stable known isotope has mass number 267. Only a few atoms have ever been made, so its bulk properties are predictions.

104RfRutherfordium[267]

Atomic number

104

protons

Atomic weight

[267]

most stable isotope

Melting point

—

Boiling point

—

Density

23.3 g/cm³

predicted

Electronegativity

—

Pauling scale

State at 25 °C

Unknown

predicted solid

Discovered

1964–1969

USSR / United States

Rutherfordium at a glance

Identity

Symbol	Rf
Atomic number (Z)	104
Atomic weight	[267] mass number of the most stable isotope
Category	Transition metal
Group	4
Period	7
Block	d-block
CAS number	53850-36-5

Atomic properties

Electron configuration	[Rn] 5f¹⁴ 6d² 7s² Full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d² 7s²
Electrons per shell	2, 8, 18, 32, 32, 10, 2
Oxidation states	+4 Less common: +3
First ionisation energy	6.02 eV (580.8 kJ/mol) 2nd: 14.35 eV · 3rd: 23.84 eV
Covalent radius	157 pm

Physical properties

State at 25 °C	Unknown (predicted solid)
Density	23.3 g/cm³ (predicted)

Isotopes & abundance

Natural occurrence	Synthetic
Radioactive	Yes
Most stable isotope	²⁶⁷Rf — half-life 2.5 h
Known isotopes	16

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

Rutherfordium electron configuration

Rutherfordium has 104 electrons. Written in short form, its ground-state configuration is [Rn] 5f¹⁴ 6d² 7s² — the electrons of the noble gas radon, plus 5f¹⁴ 6d² 7s².Written out in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d² 7s².

5f↑↓↑↓↑↓↑↓↑↓↑↓↑↓

6d↑↑

7s↑↓

Discovery and name

Discovered

1964–1969 — Joint Institute for Nuclear Research (Dubna) and Lawrence Berkeley Laboratory · USSR / United States.

Name

Ernest Rutherford.

Known for

The first transactinide element. Chemical experiments show it behaves like hafnium in group 4.

Isotopes of rutherfordium

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

Isotope	Protons	Neutrons	Half-life
²⁶⁷Rf	104	163	2.5 h

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

Rutherfordium compared with group 4

The other elements in group 4, from top to bottom of the table:

Element	Z	Atomic weight	Melting point	Boiling point	Density	Electronegativity
Titanium	22	47.867	1,670 °C	3,287 °C	4.506 g/cm³	1.54
Zirconium	40	91.222	1,854 °C	4,406 °C	6.52 g/cm³	1.33
Hafnium	72	178.49	2,233 °C	4,600 °C	13.3 g/cm³	1.3
Rutherfordium	104	[267]	—	—	23.3 g/cm³ (pred.)	—

Frequently asked questions

5 answers

What is the atomic mass of rutherfordium?

Rutherfordium has no stable isotopes, so it has no standard atomic weight. Periodic tables show [267], the mass number of its most stable known isotope.

How many protons, neutrons and electrons does rutherfordium have?

A neutral rutherfordium atom has 104 protons and 104 electrons. Its most stable isotope, rutherfordium-267, has 163 neutrons.

What is the electron configuration of rutherfordium?

[Rn] 5f¹⁴ 6d² 7s² (in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d² 7s²).

Is rutherfordium a metal?

Rutherfordium is a metal. It is in group 4, period 7.

Who discovered rutherfordium?

1964–1969 — Joint Institute for Nuclear Research (Dubna) and Lawrence Berkeley Laboratory (USSR / United States).