Fermium elements

Einsteinium, the tenth member of the actinide series, was discovered in 1952. Einsteinium and fermium (element 100) were most unexpectedly produced... 

Cwiok, S., Pashkevich, V.V., Dudek, J., Nazarevicz, W. Fission barriers of trans-fermium elements. Nucl. Phys. A410, 254-270 (1983)... 

As is well known, the effect of relativity increases when we go to superheavy elements. This term is usually applied to elements with atomic numbers above 100 (trans-fermium elements). The spectroscopic study of superheavy atoms presents a severe challenge to the experimentalist. An important relativistic effect involves changes in the level ordering. 

The use of larger particles in the cyclotron, for example carbon, nitrogen or oxygen ions, enabled elements of several units of atomic number beyond uranium to be synthesised. Einsteinium and fermium were obtained by this method and separated by ion-exchange. and indeed first identified by the appearance of their concentration peaks on the elution graph at the places expected for atomic numbers 99 and 100. The concentrations available when this was done were measured not in gcm but in atoms cm. The same elements became available in greater quantity when the first hydrogen bomb was exploded, when they were found in the fission products. Element 101, mendelevium, was made by a-particle bombardment of einsteinium, and nobelium (102) by fusion of curium and the carbon-13 isotope. 

Sixteen isotopes of fermium are known to exist. 257Fm, with a half-life of about 100.5 days, is the longest lived. 250Fm, with a half-life of 30 minutes, has been shown to be a decay product of element 254-102. Chemical identification of 250Fm confirmed the production of element 102 (nobelium). 

Each of the elements has a number of isotopes (2,4), all radioactive and some of which can be obtained in isotopicaHy pure form. More than 200 in number and mosdy synthetic in origin, they are produced by neutron or charged-particle induced transmutations (2,4). The known radioactive isotopes are distributed among the 15 elements approximately as follows actinium and thorium, 25 each protactinium, 20 uranium, neptunium, plutonium, americium, curium, californium, einsteinium, and fermium, 15 each herkelium, mendelevium, nobehum, and lawrencium, 10 each. There is frequently a need for values to be assigned for the atomic weights of the actinide elements. Any precise experimental work would require a value for the isotope or isotopic mixture being used, but where there is a purely formal demand for atomic weights, mass numbers that are chosen on the basis of half-life and availabiUty have customarily been used. A Hst of these is provided in Table 1. 

It is possible to prepare very heavy elements in thermonuclear explosions, owing to the very intense, although brief (order of a microsecond), neutron flux furnished by the explosion (3,13). Einsteinium and fermium were first produced in this way they were discovered in the fallout materials from the first thermonuclear explosion (the "Mike" shot) staged in the Pacific in November 1952. It is possible that elements having atomic numbers greater than 100 would have been found had the debris been examined very soon after the explosion. The preparative process involved is multiple neutron capture in the uranium in the device, which is followed by a sequence of beta decays. Eor example, the synthesis of EM in the Mike explosion was via the production of from followed by a long chain of short-Hved beta decays,... 

Isotopes sufficiently long-Hved for work in weighable amounts are obtainable, at least in principle, for all of the actinide elements through fermium (100) these isotopes with their half-Hves are Hsted in Table 2 (4). Not all of these are available as individual isotopes. It appears that it will always be necessary to study the elements above fermium by means of the tracer technique (except for some very special experiments) because only isotopes with short half-Hves are known. 

The effects of a rather distinct deformed shell at = 152 were clearly seen as early as 1954 in the alpha-decay energies of isotopes of californium, einsteinium, and fermium. In fact, a number of authors have suggested that the entire transuranium region is stabilized by shell effects with an influence that increases markedly with atomic number. Thus the effects of shell substmcture lead to an increase in spontaneous fission half-Hves of up to about 15 orders of magnitude for the heavy transuranium elements, the heaviest of which would otherwise have half-Hves of the order of those for a compound nucleus (lO " s or less) and not of milliseconds or longer, as found experimentally. This gives hope for the synthesis and identification of several elements beyond the present heaviest (element 109) and suggest that the peninsula of nuclei with measurable half-Hves may extend up to the island of stabiHty at Z = 114 andA = 184. 

Fermi lived only a little more than a decade after his hour of triumph. He spent most of this time at the University of Chicago, where, as in Rome, he surrounded himself with a group of outstanding gi aduate students, many of whom also later received Nobel Prizes. Fermi died of stomach cancer in 1954, but his name remains attached to many of the important contributions he made to physics. For example, element 100 is now called Fermium. 

For example, the most stable isotope of element 100, fermium, has a half-life of only 4.5 days ... 

These elements have all been named for famous scientists or for the places of their creation. For example, americium, berkelium, and californium were named after obvious geographical locations. Nobelium was named for the Nobel Institute, although later study proved it was not really created there. Curium was named for Marie Curie, the discoverer of radium. Einsteinium was named for the famous physicist, Albert Einstein. Fermium and lawrencium were named for Enrico Fermi and Ernest O. Lawrence, who made important discoveries in the field of radioactivity. Mendelevium was named for the discoverer of the periodic chart. 

Since plutonium is the actinide generating most concern at the moment this review will be concerned primarily with this element. However, in the event of the fast breeder reactors being introduced the behaviour of americium and curium will be emphasised. As neptunium is of no major concern in comparison to plutonium there has been little research conducted on its behaviour in the biosphere. This review will not discuss the behaviour of berkelium, californium, einsteinium, fermium, mendelevium, nobelium and lawrencium which are of no concern in the nuclear power programme although some of these actinides may be used in nuclear powered pacemakers. Occasionally other actinides, and some lanthanides, are referred to but merely to illustrate a particular fact of the actinides with greater clarity. 

Fermi resonance physchem In a polyatomic molecule, the relationship of two vibrational levels that have In zero approximation nearly the same energy they repel each other, and the eigenfunctions of the two states mix. fer-me, rez-3n-3ns fermium chem Asynthetic radioactive element, symbol Fm, with atomic number 100 discovered in debris of the 1952 hydrogen bomb explosion, and now made in nuclear reactors. fer-me-3m )... 

Fermium - the atomic number is 100 and the chemical symbol is Fm. The name derives from the Italian bom physicist Enrico Fermi , who built the first man made nuclear reactor. The nuchde Fm was found in the debris of a thermonuclear weapon s explosion in 1952 by a collaboration of American scientists from the Argonne National Laboratory near Chicago, Illinois, the Los Alamos Scientific Laboratory in Los Alamos, New Mexico and the University of California lab at Berkeley, California. The longest half-life associated with this unstable element is 100 day... 

The chemical characteristics of fermium are not very well known, but they are similar to its homologue erbium, the rare-earth element located just above it in the lanthanide series. 

As with most other transuranic elements of the actinide series, fermium has an oxidation state of +3, as well as possibly a +2 oxidation state. Thus, this ion can combine with nonmetals, such as oxygen and the halogens, as do many of the other elements in this series. Two examples follow ... 

The transeinsteinium actinides, fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr), are not available in weighable (> ng) quantities, so these elements are unknown in the condensed bulk phase and only a few studies of their physicochemical behavior have been reported. Neutral atoms of Fm have been studied by atomic beam magnetic resonance 47). Thermochromatography on titanium and molybdenum columns has been employed to characterize some metallic state properties of Fm and Md 61). This article will not deal with the preparation of these transeinsteinium metals. 

Fermium was formally discovered in 1954 at the Nobel Institute for Physics in Stockholm. It was synthesized in 1952 in the Material Testing Reactor in Idaho, but the discovery was not announced. The new element was named in honor of Enrico Fermi. There is no commercial application of this element because its yield is in extremely minute quantities. It has been detected in debris from thermonuclear explosion. 

The chemical properties of fermium are very similar to those of other triva-lent actinide series elements, californium and einsteinium. The element s oxidation state -1-3 is its only known oxidation state. 

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