Transition metal
Rutherfordium is a synthetic chemical element; it has symbol Rf and atomic number 104. It is named after physicist Ernest Rutherford. As a synthetic element, it is not found in nature and can only be made in a particle accelerator. It is radioactive; the most stable known isotope, 267Rf, has a half-life of about 48 minutes.
In the periodic table, it is a d-block element and the second of the fourth-row transition elements. It is in period 7 and is a group 4 element. Chemistry experiments have confirmed that rutherfordium behaves as the heavier homolog to hafnium in group 4. The chemical properties of rutherfordium are characterized only partly. They compare well with the other group 4 elements, even though some calculations had indicated that the element might show significantly different properties due to relativistic effects.
In the 1960s, small amounts of rutherfordium were produced at Joint Institute for Nuclear Research in the Soviet Union and at Lawrence Berkeley National Laboratory in California. Priority of discovery and hence the name of the element was disputed between Soviet and American scientists, and it was not until 1997 that the International Union of Pure and Applied Chemistry (IUPAC) established rutherfordium as the official name of the element.
Rutherfordium was reportedly first detected in 1964 at the Joint Institute for Nuclear Research at Dubna (Soviet Union at the time). Researchers there bombarded a 242Pu target with 22Ne ions; a spontaneous fission activity with half-life 0.3 ± 0.1 seconds was detected and assigned to 260Rf. Later work found no isotope of element 104 with this half-life, so that this assignment must be considered incorrect.
In 1966–1969, the experiment was repeated. This time, the reaction products by gradient thermochromatography after conversion to chlorides by interaction with ZrCl4. The team identified spontaneous fission activity contained within a volatile chloride portraying eka-hafnium properties.
24294Pu + 2210Ne → 264−x104Rf → 264−x104RfCl4
The researchers considered the results to support the 0.3 second half-life. Although it is now known that there is no isotope of element 104 with such a half-life, the chemistry does fit that of element 104, as chloride volatility is much greater in group 4 than in group 3 (or the actinides).
In 1969, researchers at University of California, Berkeley conclusively synthesized the element by bombarding a 249Cf target with 12C ions and measured the alpha decay of 257Rf, correlated with the daughter decay of 253No:
24998Cf + 126C → 261104Rf* → 257104Rf + 4 10n
They were unable to confirm the 0.3-second half-life for 260Rf, and instead found a 10–30 millisecond half-life for this isotope, agreeing with the modern value of 21 milliseconds. …
Very few properties of rutherfordium or its compounds have been measured; this is due to its extremely limited and expensive production and the fact that rutherfordium (and its parents) decays very quickly. A few singular chemistry-related properties have been measured, but properties of rutherfordium metal remain unknown and only predictions are available.
Rutherfordium is the first transactinide element and the second member of the 6d series of transition metals. Calculations on its ionization potentials, atomic radius, as well as radii, orbital energies, and ground levels of its ionized states are similar to that of hafnium and very different from that of lead. Therefore, it was concluded that rutherfordium's basic properties will resemble those of other group 4 elements, below titanium, zirconium, and hafnium. Some of its properties were determined by gas-phase experiments and aqueous chemistry. The oxidation state +4 is the only stable state for the latter two elements and therefore rutherfordium should also exhibit a stable +4 state. In addition, rutherfordium is also expected to be able to form a less stable +3 state. The standard reduction potential of the Rf4+/Rf couple is predicted to be higher than −1.7 V. …
Rutherfordium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Seventeen different isotopes have been reported with atomic masses from 252 to 270 (with the exceptions of 264 and 269). Most of these decay predominantly through spontaneous fission, particularly isotopes with even neutron numbers, while some of the lighter isotopes with odd neutron numbers also have significant alpha decay branches.
Out of isotopes whose half-lives are known, the lighter isotopes usually have shorter half-lives. The three lightest known isotopes have half-lives of under 50 μs, with the lightest reported isotope 252Rf having a half-life shorter than one microsecond. The isotopes 256Rf, 258Rf, 260Rf are more stable at around 10 ms; 255Rf, 257Rf, 259Rf, and 262Rf live between 1 and 5 seconds; and 261Rf, 265Rf, and 263Rf are more stable, at around 1.1, 1.5, and 10 minutes respectively. The most stable known isotope, 267Rf, is one of the heaviest, and has a half-life of about 48 minutes. Rutherfordium isotopes with an odd neutron number tend to have longer half-lives than their even–even neighbors because the odd neutron provides additional hindrance against spontaneous fission.
The lightest isotopes were synthesized by direct fusion between two lighter nuclei and as decay products. …