Rutherfordium (Rf)

Rutherfordium was the first element past the actinides, and confirming that it behaves like a group 4 metal — forming a volatile chloride the way zirconium and hafnium do — was the first real test of whether the periodic table keeps working this far out. It also began the Transfermium Wars, a twenty-year dispute between Berkeley and Dubna over who had discovered what, which IUPAC only settled in 1997 by handing out names in a package deal. Berkeley wanted to call it rutherfordium, Dubna wanted kurchatovium, and for decades Soviet and Western textbooks printed different periodic tables.

Properties

Atomic number

104

Symbol

Rf

Mass number of most stable isotope

[267]

Category

Transition metal

Group

4

Period

7

Block

d-block

Electron configuration

[Rn] 7s² 5f¹⁴ 6d²

Electrons per shell

2, 8, 18, 32, 32, 10, 2

Oxidation states

+4

Discovered

1964 by Dubna, with independent work at Berkeley in 1969; IUPAC credited both

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d²

Noble gas shorthand

[Rn] 7s² 5f¹⁴ 6d²

Shells

K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 10 · Q: 2

What it is used for

• Research only; no application outside the laboratory

Hazards

• Intensely radioactive; exists only as individual atoms in an accelerator

Melting point, boiling point, density and electronegativity are omitted: no measurement is possible on the quantities that exist. The mass given is the mass number of rutherfordium-267, the longest-lived at roughly 1.3 hours.

Several physical properties are not listed for rutherfordium because no bulk sample has ever existed. Only a handful of atoms have been produced, often with half-lives measured in seconds, so published melting points and densities for elements in this range are calculations rather than measurements. They are omitted rather than presented as observed values.

Neighbours in the table

Group 4

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Rutherfordium sits in group 4 with titanium, zirconium, hafnium.