Mendelevium elements

In 1961, enough einsteinium was produced to separate a macroscopic amount of 253Es. This sample weighted about O.OlMg and was measured using a special magnetic-type balance. 253Es so produced was used to produce mendelevium (Element 101). 

The discovery of mendelevium, element 101, demanded some fancy footwork on the part of the chemists involved because mendelevium has a half-life of only about half an hour. It was distinctly a matter of chemistry-on-the-run. 

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. 

Dmitri Mendeleev) Mendelevium, the ninth transuranium element of the actinide series discovered, was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment of the isotope 253Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was 256Md, which has a half-life of 76 min. This first identification was notable in that 256Md was synthesized on a one-atom-at-a-time basis. 

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. 

The other actinides have been synthesized in the laboratory by nuclear reactions. Their stability decreases rapidly with increasing atomic number. The longest lived isotope of nobelium (102N0) has a half-life of about 3 minutes that is, in 3 minutes half of the sample decomposes. Nobelium and the preceding element, mendelevium (ioiMd), were identified in samples containing one to three atoms of No or Md. 

Element 101 is named Mendelevium in honor of the great Russian chemist, Dmitri Mendeleev. The youngest of seventeen children, he was born in Tobolslca where his grandfather published the first newspaper in Siberia and his father ivaj the high school principal. Dmitri received his early education from a political exile, but when his father died, his mother traveled west in search of better educational opportunities for Dmitri. 

Mendeleev, Dimitri, 104,107 Mendelevium, oxidation number, 414 Mercuric perchlorate, 237 Mercurous perchlorate, 237 Mercury, oxidation numbers, 414 Mercury (planet), data on, 444 Metabolism, oxidative, 429 Metallic alloys, 309 bond, 303 elements. 303 radius, 380 substances, 81 Metals alkali, 94... 

The names of all the elements and their symbols are shown in the tables in the back of this book. Most of the symbols match up with the names H for hydrogen, 0 for oxygen, C for carbon. He for helium, Li for lithium. Symbols for the newer elements are easy to interpret, too. Element 101, for instance, has the symbol Md and the well-deserved name of Mendelevium. But a few of the symbols in the periodic table do not match the names of their elements. Sodium, for instance, does not have the symbol So. Instead, it is Na. Potassium isn t Po, but rather K. 

Die Entdeckung des Elementes 101, Mendelevium Mv, wurde kiirzlich be-kanntgegeben [32). Man erhielt es durch BeschuB von Element 99 mit a-Teilchon im Cyclotron nach ... 

Seaborg New element Mendelevium, atomic number 101. Physic. Rev. 98, 1518 (1955). 

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. 

Mendelevium - the atomic number is 101 and the chemical symbol is Md. The original chemical symbol proposed was Mv but this was changed in 1955. The element name derives from the... 

Before their experiment that produced mendelevium, the team had speculated that this element number 101 must be somewhat similar to the element thulium ( Tm) located just above it in the lanthanide series. Because they did not have a name for this new element, they referred to it as eka-thuhum, with an atomic number of 101. It was formally named mendelevium in 1955 only after they were able to produce a few atoms of einsteinium by the nuclear process as follows gjEs-253 + —> Md-256 + n-1 (a neutron with a mass of... 

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. 

In 1955 Albert Ghiorso and his colleagues at the University of California at Berkeley discovered the artificial element mendelevium. The scientists produced mendelevium one atom at a time, getting 17 atoms in all. Mendelevium was added to the periodic table as element number 101. 

The element first was made by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in 1955 in Berkeley, California. It was synthesized by bombardment of einsteinium-253 with alpha particles of 41 MeV energy in a 60-inch cyclotron. The element was named Mendelevium in honor of Russian chemist Dimitri Mendeleev. Mendelevium —258 isotope with a half-life of 60 days was discovered in 1967. The element has no commercial use except in research to synthesize isotopes of other transuranium elements. 

Shortly after the announcement of the naming of berkelium A. P. Znoiko in Russia, who had made earlier predictions of the properties of element 97, suggested that Mendeleev should be honored by giving his name to this element, calling it mendelevium (95). The name berkelium had already been adopted, but, as will be seen, at the first opportunity the Berkeley group did honor the father of the periodic table. 

In 1955 the next step was announced. Very intense helium ion bombardment of tiny targets of E253 produced a few spontaneously fissionable atoms which eluted from ion-exchange resins in the eka-thulium position. This was evidence that element 101 had been found. Only seventeen atoms of this element were produced. It showed a half-life of between one-half and several hours. The name mendelevium (symbol... 

As these superheavy elements get heavier, they become less stable the nuclei sit around for progressively shorter times before undergoing radioactive decay. Plutonium-239 has a half-life of 24,000 years, which means that it takes this long for half the atoms in a sample of Pu to decay. Califomium-249 (element 98) has a half-life of350 years mendelevium-258 (lOl), fifty-one days seaborgium-266 (106) twenty-one seconds. Isotope 272 of element 111 has a fleeting existence with a half-life of 1.5 milliseconds, and that of isotope 277 of element 112, made in 1996, is less than a third of a millisecond. This is one reason why it becomes increasingly hard to make and see these superheavy elements. ... 

TRANSACTINIUM EARTHS. A group of chemical elements more frequently termed the Actinides. In order of increasing atomic number, they indude actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium. and lawrencium. See also Actinide Contraction. 

The years after World War II led to the discovery of elements 97-103 and the completion of the actinide series. While the story of the discovery of each of these elements is fascinating, we shall, in the interests of brevity, refer the reader elsewhere (see References) for detailed accounts of most of these discoveries. As an example of the techniques involved, we shall discuss the discovery of element 101 (mendelevium). 

There no fixed rule for naming elements. Some names of elements take the names of scientists (Mendelevium, Md Rontgenium, Rg...), places (Americium, Am Europium, Eu...), and the names of planets (Uranium, U Plutonium, Pu...). Some names come from mythology (Titanium, Ti Thorium, Th...) or properties of the element (eg hydrogen means water former, oxygen means acid former). 

When Mendeleev published his periodic table for the first time, there were 63 elements. After his death, the number of elements had increased to 86. This quick increase was the result of the periodic table, the most important systemization of chemistry. Although Mendeleev did not discover any new elements, the element with the atomic number 101 discovered by a committee of American scientists led by G.T Seaborg in 1955, was named mendelevium (Md) in honor of Dmitri Mendeleev. 

The 100th element of the expanded Periodic Table was first sighted in the dust of a nuclear explosion set off in 1952 at Eniwetok atoll in the Pacific. When Enrico Fermi, one of great builders of the atomic age, was killed by cancer late in 1954, his fame was immortalized in the name of this new element, fermium. Finally, element No. 101 was created out of element 99 and named mendelevium. But this is not the end of element creation, for Seaborg predicated that within the next few years at least seven more elements would be synthesized. 

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