Rutherfordium (Rf)
Element 104 · Transition metal · atomic mass [267] u · group 4, period 7
Electron shells: 2, 8, 18, 32, 32, 10, 2
Rutherfordium is the first transactinide and the first element where relativistic effects noticeably distort the chemistry you would predict from the table. Its longest-lived isotope survives about an hour.
It behaves chemically like hafnium, confirming the periodic table still works past element 103.
- Atomic number
- 104
- Atomic mass
- [267] u
- Electron configuration
- [Rn] 7s² 5f¹⁴ 6d²
- Group · period · block
- 4 · 7 · d
- Oxidation states
- +4
- Electronegativity
- Not measured
- Melting point
- —
- Boiling point
- —
- Density
- Not measured
- State at 20 °C
- Unknown
- Appearance
- Unknown; presumed metallic
- Discovered
- Joint Institute for Nuclear Research and Lawrence Berkeley Laboratory, 1964
104 protons, and 104 electrons when neutral
Mass number of the longest-lived isotope — no standard atomic weight exists
Titanium group
What Rutherfordium is used for
- Scientific research only
Atomic structure of Rutherfordium
A neutral rutherfordium atom has 104 protons and 104 electrons. Its most common isotope carries about 163 neutrons, which is where the mass number 267 comes from. Change the neutron count and you have a different isotope of rutherfordium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 32, 10, 2. In orbital notation that is [Rn] 7s² 5f¹⁴ 6d². As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Rutherfordium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Rutherfordium sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
- Directly above: Hafnium — same group, so similar chemistry with a smaller atom.
- One proton lighter: Lawrencium.
- One proton heavier: Dubnium.
Discovery and naming
Rutherfordium was discovered by Joint Institute for Nuclear Research and Lawrence Berkeley Laboratory in 1964. Its name comes from Ernest Rutherford, which is also why its symbol (Rf) does not match its English name.
Every isotope of rutherfordium is radioactive, so it has no standard atomic weight. Periodic tables show the mass number of its longest-lived isotope in square brackets instead.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Rutherfordium?
Rutherfordium has no stable isotope, so it has no standard atomic weight. Periodic tables instead show 267 in square brackets — the mass number of its longest-lived isotope.
How many protons, neutrons and electrons does Rutherfordium have?
Rutherfordium has 104 protons, because the atomic number is the proton count and that is what makes an atom Rutherfordium at all. A neutral Rutherfordium atom has the same number of electrons, 104. The neutron count varies by isotope; the most common one has about 163, since 267 − 104 = 163.
What is the electron configuration of Rutherfordium?
The electron configuration of Rutherfordium is [Rn] 7s² 5f¹⁴ 6d². Its electrons are arranged 2, 8, 18, 32, 32, 10, 2 across 7 shells.
Is Rutherfordium a metal?
Yes. Rutherfordium is classified as a transition metal, on the metallic side of the table.
What group and period is Rutherfordium in?
Rutherfordium is in group 4 (the titanium group), period 7, in the d-block. The group is its column and the period is its row.
What is the charge of Rutherfordium?
Rutherfordium most commonly forms a 4+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is Rutherfordium used for?
Scientific research only. Rutherfordium is the first transactinide and the first element where relativistic effects noticeably distort the chemistry you would predict from the table.
Who discovered Rutherfordium, and where does its name come from?
Rutherfordium (Rf) was discovered by Joint Institute for Nuclear Research and Lawrence Berkeley Laboratory in 1964. The name comes from Ernest Rutherford.
Is Rutherfordium radioactive?
Yes. Every isotope of Rutherfordium is radioactive — it has no stable form at all, which is why the periodic table shows its mass in square brackets rather than as a standard atomic weight.