Group of chemical elements

Two groups of chemical elements can be considered related to their distribution in soil profiles. The first group includes the essential nutrients actively absorbed by vegetation and relatively tightly bound in soil organic matter (Figure 11). 

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. 

Certainly it is possible to apply also other display methods for the visualization of such complex environmental data, as particulate emissions. TREIGER et al. [1993 1994] describe the study of different aerosol samples by nonlinear mapping of electron probe microanalysis data. Different interpretable groups of chemical elements which determine the composition of aerosol samples can be obtained. More recent work by WIENKE and HOPKE [1994] and WIENKE et al. [1994] discuss the combination of different chemometric techniques for better graphical representation of aerosol particle data. The authors use receptor modeling with a minimal spanning tree combined with a neural network. 

The vertical coluiniis of the periodic table, with connections between the short and long periods as shown, are the groups of chemical elements. Elements in the same group may be called congeners these elements have closely related physical and chemical properties. 

The third group of chemical elements reviewed in this chapter comprises two precious metals, silver and gold, plus the sextet of Pt metals ruthenium, rhodium, palladium, osmium, iridium and platinum. Considered will be also some less frequent heavy metals, i.e. antimony, bismuth, indium, tin (by some authors... 

The actinide elements are a group of chemically similar elements with atomic numbers 89 through 103 and their names, symbols, atomic numbers, and discoverers are given in Table 1 (1-3) (see Thorium and thorium compounds Uranium and uranium compounds Plutonium and plutonium compounds Nuclear reactors and Radioisotopes). 

Perhaps the earliest hints of any numerical regularity among the atomic weights of the elements was discovered as early as 1817 by Dobereiner. He was the first to notice the existence of various groups of three elements, subsequently called triads, that showed chemical similarities. In addition, such elements displayed an important numerical relationship, namely that the equivalent weight, or atomic weight, of the middle element is the approximate mean of the values of the two flanking elements in the triad. 

Increasingly, new attempts to use basic chemistry to separate substances from radioactive material were meeting with failure. In many cases, two substances which were known to have different radioactive properties and molecular masses simply could not be separated from one another and appeared chemically identical. By 1910, this problem led Soddy to speculate that there were different forms of the same element (Soddy 1910). By 1913 he was confident of this interpretation and coined the term isotope to describe the various types of each element, recognizing that each isotope had a distinct mass and half-life (Soddy 1913b). In the same year he wrote that radiothorium, ionium, thorium, U-X, and radioactinium are a group of isotopic elements, the calculated atomic masses of which vary from 228-234 (a completely accurate statement- we now call these isotopes Th, °Th, Th, Th respectively). Soddy received the... 

The origin of chemical elements has been explained by various nuclear synthesis routes, such as hydrogen or helium burning, and a-, e-, s-, r-, p- and x-processes. "Tc is believed to be synthesized by the s (slow)-process in stars. This process involves successive neutron capture and / decay at relatively low neutron densities neutron capture rates in this process are slow as compared to /1-decay rates. The nuclides near the -stability line are formed from the iron group to bismuth. 

Period 5 (group 3 [IIIB] to group 12 [IIB]) is located in the second row of the transition elements and represents 10 of the transition metals to nonmetals found in the periodical table of chemical elements. This period is also known to include some of the so-called rare-earth elements. Most of the rare-earths are found in the lanthanide series, which follows barium (period 6, group 3). (Check the periodic table to locate the major rare-earth elements in the lanthanide series. These are addressed in a later section of the book.)... 

Osmium is found in group 8 (VIII) of the periodic table and has some of the same chemical, physical, and historical characteristics as several other elements. This group of similar elements is classed as the platinum group, which includes Ru, Rh, and Pd of the second transition series (period 5) and Os, Ir, and Pt of the third series of transition metals (period 6). 

The halogens are the family of nonmetal elements in group 17 (VIIA) that are located just to the right of the oxygen group 16 on the periodic table of chemical elements. They are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). 

Isotopes are thus a kind of free give-away bonus to the Periodic Table. In a sense they expand our choice of elements by giving us extra versions that do unique and useful things. We do well to remember that each entry in the table represents not a sole member of the element family but a kind of averaged image of a small group of chemical brothers and sisters, each with their own talents. 

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