Elements manmade

Symbol Es atomic number 99 atomic weight 252 a radioactive transuranium, actinide series, manmade element electron configuration [Rn]5/ i7s2 the most stable isotope Es-254. Isotopes, their half-lives and the mode of decay are as follows ... 

The chemical behavior of the transuranium elements is interesting because of its complexity and the insights offered into the chemistry of the lighter elements. The placing of these manmade elements into the periodic table (Fig. 15.1) represents one of the few significant alterations of the original periodic table of Mendelyeev. Since so little is known about the chemistry of the transactinide elements, one has the unique opportunity to test periodic table predictions of chemical behavior before the relevant experiments are done. 

Radioisotopes that decay by spontaneous fission with the direct accompanying release of neutrons are usually associated with the natural elements of uranium and thorium and the manmade element plutonium. However, the rate of decay of these elements by fission is so slow that it is only by incorporating them into large nuclear piles or chain reactors that they can be utilized as intense neutron sources. In the US Dept of Energy National Transplutonium Program, small quantities of elements heavier than plutonium are produced for basic research studies and to discover new elements with useful properties. One of these new elements, californium-252 (2S2Cf), is unique in that it emits neutrons in copious quantities over a period of years by spontaneous fission... 

Elements with atomic numbers ranging from 90 to 103, the actinides, are members of a transition series in which the first member is actinum (atomic number 89). They are analogues to lanthanides and occupy the same part of the Periodic Table at the next period. Only four of them have been found in nature the others are manmade elements produced by neutron irradiation or heavy-ion bombardment. All of them are radioactive [282]. Technetium (element 43), although not part of the actinides series, possesses two radioactive isotopes with long half-lives "Tc (2.12 x 105s, has the practical use) and 98Tc (1.5 x 106 years, a rhenium analogue) [283],... 

Transuranium—Term given to all the manmade elements of greater atomic number than 92. 

There are 90 naturally occurring and 20 manmade elements. Not all of the elements on the Periodic Table are common or particularly hazardous to responders. There are, however, some 39 elements that we will call the HazMat elements. These elements are important to the study of the chemistry of hazardous materials. Most... 

Chemists make compounds and strive to understand their reactions. My own interest lies in the chemistry of the compounds of the elements carbon and hydrogen, called hydrocarbons. These make up petroleum oil and natural gas and thus are in many ways essential for everyday life. They generate energy and heat our houses, fuel our cars and airplanes and are raw materials for most manmade materials ranging from plastics to pharmaceuticals. Many of the chemical reactions essential to hydrocarbons are catalyzed by acids and proceed through positive ion intermediates, called carbocations. 

Prior to 1940 only the naturally occurring actinides (thorium, protactinium and uranium) were known the remainder have been produced artificially since then. The transactinides are still being synthesized and so far the nine elements with atomic numbers 104-112 have been reliably established. Indeed, the 20 manmade transuranium elements together with technetium and promethium now constitute one-fifth of all the known chemical elements. 

About half the manmade emissions of sulfur dioxide become sulfate aerosol. That implies that currently 35 Tg per year of sulfur in sulfur dioxide is converted chemically to sulfate. Because the molecular weight of sulfate is three times that of elemental sulfur, Q is about 105 Tg per year. Studies of sulfate in acid rain have shown that sulfates persist in the air for about five days, or 0.014 year. The area of the Earth is 5.1 x lO m. Substituting these values into the equation for B yields about 2.8 X 10 g/m for the burden. 

The chemical elements are the building blocks of nature. All substances are combinations of these elements. There are (as of 2005) 113 known chemical elements with the heaviest naturally occurring element being uranium (Z = 92). The 22 heaviest chemical elements, the transuranium elements, are manmade. The story of their synthesis, their properties, their impact on chemistry and physics, and their importance to society is fascinating. This story is of particular importance to nuclear chemistry because most of our knowledge of these elements and their properties comes from the work of nuclear chemists, and such work continues to be a major area of nuclear chemical research. One of us (GTS) has been intimately involved in the discovery and characterization of these transuranium elements. 

In the periodic table, the last naturally occurring element is element 92, uranium (U). Uranium is a radioactive element. Radioactive elements are unstable and break down to form lighter elements and in the process give off energy. All of the elements that occur past uranium are manmade, and are referred to collectively as the transuranium elements. 

The largest area of change in the periodic table will come from the manmade creation of new chemical elements. Every element past uranium in the periodic table has been made by scientists in high energy particle accelerators. The first transuranium element made was element 93, discovered by E. M. Macmillan and P. H. Abelam at the University of California at Berkeley in 1940. The two discoverers of this element named it neptunium (Np). 

Recently, several new manmade superheavy elements have been discovered. These include elements 110 and 111, both of which were made in late 1994 by an international team of scientists. These scientists performed this research at GSI, a research center for heavy ion research in Darmstadt, Germany. Element 110 was made by colliding nickel atoms with an isotope of lead. Researchers in Russia have plans to make a different isotope of element 110 by colliding sulfur atoms with plutonium atoms. Elements 116 and 118 were recently discovered at a Berkeley laboratory. Other superheavy elements which have been predicted to exist have yet to be made in the laboratory, although research continues into the creation of these elements. 

The purpose of this paper is to present data on the environmental behavior of selected actinide elements. Environmental chemistry factors that influence the mobility of these elements are discussed. Some of the variability of data on the uptake of actinide elements by plants is explained. The behavior of manmade actinides in a representative aquatic environment is also discussed. Except for general comparisons, exposure of man by the inhalation pathway is not considered in this paper, even though higher exposures are routinely calculated for this pathway relative to the ingestion pathway. 

Selenium belongs to Group VIA of the Periodic Table of the elements, and is located between sulfur and tellurium. Its chemical and physical properties are intermediate between those of a metal and a nonmetal. Furthermore, selenium resembles sulfur more closely than tellurium. The atomic number and atomic mass of the element are 34 and 78.96, respectively there are six natural isotopes, Se, Se, Se, Se, Se, Se, whose abundance is 0.87, 9.02, 7.58, 23.52, 49.82, and 9.19%, respectively. Additionally, there are ten short-lived manmade isotopes of which Se, Se, and Se are the most utilized in neutron activation analysis and radiology (Newland... 

The analysis of natural radioactive materials is relatively straightforward, since it usually involves the determination of a small number of well-known radioisotopes of a few elements. The determination of manmade radionuclides in air samples is more complicated, because several radionuclides of a number of elements may be involved both qualitative and quantitative studies may be needed, and carriers may have to be identified. 

Hydrocarbon-derivative compounds do not occur naturally. They are manmade from hydrocarbon compounds, as discussed earlier, with some additional elements added. Hydrocarbon derivatives belong to families just as the hydrocarbons. In order to make hydrocarbon derivatives, hydrogen needs to be removed from the alkane family. Alkene hydrocarbons have one or more double bonds that can be broken and... 

Elements above lead (atomic numbers 83 and above) on the Periodic Table are radioactive (see Figure 9.2). Other elements may have one or more radioactive isotopes. Some elements occur naturally, while others are manmade. Each symbol on the Periodic Table represents one atom of that element. An atom is made up of a nucleus with varying numbers of electrons in orbits circling around the nucleus (see Figure 9.3). Located inside the nucleus are protons and neutrons. Protons in the nucleus of an atom represent the atomic number of that element. Neutron numbers may vary within the same type of element or from one element to another, but the number of protons must stay the same. The atom is the smallest part of an element that normally exists so any particle of an element that is smaller than an atom is commonly referred to as a subatomic particle. 

People are exposed to small amounts of radiation every day, both from naturally occurring sources such as elements in the soil or cosmic rays from the sun), and man-made sources. Manmade sources include some electronic equipment (such as microwave ovens and television sets), medical sources (such as x-rays, certain diagnostic tests, and treatments), and from nuclear weapons testing. 

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