FROM THE CURRENT LITERATURE

DISCOVERY OF ELEMENT No. 102

On July 9 of this year it was officially announced that, through the efforts of scientists from three countries—Sweden, the USA, and England—a new chemical element, No. 102, had been artificially produced. Taking part in the work on the synthesis of the new element were H. Atterling, W. Forsling, L. Holm, and B. Åström (Sweden: Nobel Institute of Physics in Stockholm), P. Fields and A. Friedman (USA: Argonne National Laboratory), D. Milsted and A. Bidl (England: Atomic Energy Research Establishment at Harwell).

Element No. 102 was obtained as a result of bombarding the isotope curium \( \mathrm{Cm}^{244} \) with ions of the isotope carbon \( \mathrm{C}^{13} \), as a result of the nuclear reaction
\( {}_{96}\mathrm{Cm}^{244}+{}_{6}\mathrm{C}^{13}\to 102^{251}+6n \)
(or \(102^{253}+4n\)). The \( \mathrm{Cm}^{244} \) used as the starting material was obtained in the reactor of the Argonne Laboratory, and the irradiation target (a thin film of curium on an aluminum backing) was prepared at Harwell. There, too, the amount of isotope needed for the ion source of the Stockholm cyclotron was prepared.

The irradiation itself was carried out in the cyclotron of the Nobel Institute in Stockholm. The \( \mathrm{C}^{13} \) ion current was approximately \(0.2\,\mu a\), and the irradiation time varied from 5 to 30 min and in most cases was 20 min. The nuclei of atoms of the new element, owing to recoil energy, flew out of the target and were collected on thin organic films. After irradiation, these films were dissolved on a platinum plate in a drop of acetone. When the acetone was evaporated, the atoms of the reaction product remained on the surface and were then examined with an α-particle pulse analyzer. To study the chemical properties of this product, the platinum plate was treated with hydrochloric acid, with the activity being transferred into the solution. Then the compound containing atoms of the new element was separated on an ion-exchange column (filled with cation-exchange resin) by elution with α-hydroxyisobutyric acid.

The time from the end of irradiation to the investigation of the activity with the aid of the pulse analyzer was 2–3 min; separation of the irradiation products on the ion-exchange column required another 7 minutes. The isotope of the new element obtained—\(102^{251}\) (or \(102^{253}\))—emits α-particles with an energy of about \(8.5\,\mathrm{Mev}\) and has a half-life of about 10 min. It is not excluded, however, that the observed α-decay is undergone already by the daughter isotope of mendelevium \( \mathrm{Mv}^{251} \) (or \( \mathrm{Mv}^{253} \)), formed as a result of rapid \(K\)-capture in atoms of the original isotope of element No. 102.

In July of this year, at the Paris meeting of the International Union of Pure and Applied Chemistry, a decision by the nomenclature commission on inorganic chemistry was announced approving the name of the new element—nobelium (symbol—No)—in honor of the name borne by the institute where element No. 102 was first synthesized.

There it was also announced that new symbols had been approved for argon (Ar instead of A) and element No. 99—einsteinium (Es instead of E). Henceforth, the symbols of elements will be given either by the first letters or by the first letters of the first and second syllables of the element name.

REFERENCES

1. Science News Letter 72, No. 3, 35 and No. 6, 83, 1957.
2. Nature 4577, 120, 1957.
3. Engineering, 4768, 124, 1957.
4. Chem. Eng. News 35, 287, 1957.