# Transuranic elements

The transuranic elements are the elements with a higher atomic number than uranium (greater than 92).

## properties

All transuranic elements are radioactive with half-lives between a few tens of millions of years (rare, e.g. plutonium-244 ) over minutes to fractions of a second (often). Some isotopes of the lighter transuranic elements from Neptunium to Curium have half-lives of a few millions, millennia or centuries. They arise in nuclear reactors and make up part of the long-lived radioactive waste.

After the uranium with atomic number 92, the series of transuranic elements begins with neptunium (element 93). In addition to the element plutonium (94), which is important for nuclear fission , americium (95), curium (96), berkelium (97), californium (98), einsteinium (99), fermium (100), mendelevium (101), nobelium ( 102) and Lawrencium (103) as well as all other heavier elements ( transactinoids ) belonging to the transuranic elements.

The transuranic elements named here were produced and characterized in the working group headed by Glenn T. Seaborg ; Seaborg received the Nobel Prize in Chemistry for this in 1951 .

Up to and including element 103, lawrencium , they belong to the group of actinides together with thorium (90), protactinium (91) and uranium (92) .

## Occurrence and extraction

When a weakly enriched fuel element burns down (left), the proportion of 238 U sinks , which also results in transuranic elements

Due to the short half-life periods seen from a geological point of view, transuranic elements do not occur in nature or only occur in traces that result from neutron capture and subsequent beta decay of uranium, e.g. B .:

${\ displaystyle \ mathrm {^ {238} _ {\ 92} U \ + \ _ {0} ^ {1} n \ \ longrightarrow \ _ {\ 92} ^ {239} U \ {\ xrightarrow [{23, 5 \ min}] {\ beta ^ {-}}} \ _ {\ 93} ^ {239} Np \ {\ xrightarrow [{2,3565 \ d}] {\ beta ^ {-}}} \ _ { \ 94} ^ {239} Pu}}$
The times given are half-lives .

The only exception is plutonium 244 Pu, which dates back to the time the solar system was formed.

Transuranium elements can be technically produced from uranium or other elements with a high atomic number. For this purpose, such atomic nuclei are bombarded with neutrons or other atomic nuclei; The neutron capture and subsequent beta decay that occurs produce transuranic elements.

## Original meaning of the word

Originally, Transuran was a shorter term for an artificial super-heavy element . The tiniest traces of plutonium-244 from the time the solar system was formed was only discovered in 1971, long after the term transuranic was coined . In the original meaning one would therefore have to speak of transplutonium elements today.

## Research history

Mendeleev's periodic table from 1871 with a gap for Neptunium at the bottom, behind uranium ( U = 240 )

Already in Mendeleev's periodic table of elements from 1871 there was a gap behind uranium, the heaviest known element at the time.

More than sixty years later, Ida Noddack commented in May 1934 on the gaps in Mendeleev's periodic table that existed at the time and, at the end of her work, considered the possibility of transuranics. A few weeks later, Enrico Fermi published three papers on this topic. In September 1934, Noddack took a critical look at the supposed discovery of element 93 by Fermi. In her remarks she took u. a. the discovery of neutron-induced nuclear fission in advance: “It is conceivable that when heavy nuclei are bombarded with neutrons, these nuclei disintegrate into several larger fragments, which are isotopes of known elements, but not neighbors of the irradiated elements. “Regardless of Noddack's objections, at that time all working groups followed the hypothesis that irradiating uranium with neutrons always produced elements heavier than uranium.

At the Kaiser Wilhelm Institute for Chemistry in Berlin , Otto Hahn , Fritz Straßmann and Lise Meitner also went in search of transuranium elements during this time. Over many years they tried to elucidate the processes observed in Fermi's experiments. While searching for heavier elements, they found some substances that they described as evidence of transuranium elements.

Irène Joliot-Curie and Paul Savitch also devoted themselves to the search for transurans in Paris from 1937 onwards . In 1937/1938 her working group carried out experiments in which an element similar to lanthanum was released, the chemical identification of which turned out to be extremely difficult and which they interpreted as a possible evidence of element 93 based on the assumptions about chemical relationships at the time. They considered it possible that the substance discovered “ has an atomic number of 93 and that the transuranic elements found by Hahn, Meitner and Straßmann to date are elements 94 to 97. "

In fact, the observations made by Hahn, Straßmann, Meitner, Joliot-Curie and Savitch were not evidence of the transuranic elements they were looking for, but rather the nuclear fission of uranium, which was still unrecognized at the time . Their research therefore contributed comparatively little to the knowledge about the chemical element later called "neptunium", since they considered the numerous fission products formed during the nuclear fission of uranium to be evidence of the sought-after transuranic elements and described them as such in their publications.

## literature

• AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
• Lester R. Morss, Norman M. Edelstein, Jean Fuger: The Chemistry of the Actinide and Transactinide Elements , Dordrecht 2006, ISBN 1-4020-3555-1 .
• Glenn T. Seaborg: Transuranium Elements: A Half Century; Literature information ; ( online , PDF, 6.5 MiB)
• Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: Traces of transuranium elements in terrestrial minerals? ( online , PDF, 492 KiB)
• Christian Schnier, Joachim Feuerborn, Bong-Jun Lee: The search for super heavy elements (SHE) in terrestrial minerals using XRF with high energy synchrotron radiation. ( Online , PDF file, 446 kB)

## Individual evidence

1. ^ A b D. C. Hoffman, FO Lawrence, JL Mewherter, FM Rourke: "Detection of Plutonium-244 in Nature", in: Nature 1971 , 234 , pp. 132-134 ( doi : 10.1038 / 234132a0 ).
2. Ida Noddack: The Periodic System of the Elements and its gaps , in: Angewandte Chemie , 1934 , 47  (20), pp. 301-305 ( doi: 10.1002 / ange.19340472002 ).
3. ^ E. Fermi: Radioactivity Induced by Neutron Bombardment , in: Nature , 1934 , 133 , pp. 757-757 ( doi: 10.1038 / 133757a0 ).
4. E. Fermi: Element No. 93 , in: Nature , 1934 , 133 , pp. 863-864 ( doi: 10.1038 / 133863e0 ).
5. ^ E. Fermi: Possible Production of Elements of Atomic Number Higher than 92 , in: Nature , 1934 , 133 , pp. 898-899 ( doi: 10.1038 / 133898a0 ).
6. Ida Noddack: About the element 93 , in: Angewandte Chemie , 1934 , 47  (37), pp. 653-655 ( doi: 10.1002 / anie.19340473707 ).
7. ^ I. Curie, P. Savitch: Sur les radioéléments formés dans l'uranium irradié par les neutrons II . Le Journal de Physique et le Radium 9 (1938) pp. 355-359.