Element stable

Radioactive elements may often be prepared artificially by bombarding the atoms of ordinary stable elements with, e.g. helium nuclei. See radioactivity, artificial. 

In its simplest form, a mass spectrometer is an instmment that measures the mass-to-charge ratios ml of ions formed when a sample is ionized by one of a number of different ionization methods (1). If some of the sample molecules are singly ionized and reach the ion detector without fragmenting, then the ml ratio of these ions gives a direct measurement of the molecular weight. The first instmment for positive ray analysis was built by Thompson (2) in 1913 to show the existence of isotopic forms of the stable elements. Later, mass spectrometers were used for precision measurements of ionic mass and abundances (3,4). 

The word calcium is derived from calx, the Latin word for lime. The Romans used large quantities of calcium oxide or lime as mortar in constmction (see Lime and limestone). Because calcium compounds are very stable, elemental calcium was not produced until 1808 when a mercury amalgam resulted from electrolysis of calcium chloride in the presence of a mercury cathode. However, attempts to isolate the pure metal by distilling the mercury were only marginally successful. 

C. C. Ahn, O. L. Krivanek EELS Atlas -A Reference Guide of Electron Energy Loss Spectra Covering All Stable Elements, GATAN Inc. 

Decay The spontaneous disintegration of an unstable atomic nucleus to form another more stable element or isotope of a lower atomic mass. 

Radioactive transformations are accomplished by several different mechanisms, most importantly alpha ptirticle, beta particle, tuid gamma ray emissions, Each of tliese mechanisms are sponuuieous nuclear transformations. The result of these transformations is tlie formation of different tuid more stable elements. 

Several different mechanisms, most importtuitly alplia particle, beta particle, and gamma ray emissions accomplish radioactive transformations. Each of these mechanisms is a spontaneous nuclear transformation. Tlie result of tliese transformations is the formation of different stable elements. Tlie kind of transformation that will ttike place for any given radioactive element is a function of the type of nuclear inslabilitv as well as the mass/energy relationship. The nuclear instability is dependent on the ratio of neutrons to... 

Pencil lead" is almost pure graphite. Graphite is the stable elemental form of carbon at 25°C and 1 atm. Diamond is an allotrope of graphite. Given... 

This can result in a radioactive product from the A(n, t)A reaction where A is the stable element, n is a thermal neutron, A is the radioactive product of one atomic mass unit greater than A, and y is the prompt gamma ray resulting from the reaction. A is usually a beta and/or gamma emitter of reasonably long half-life. Where access to a nuclear reactor has been convenient, thermal neutron activation analysis has proven to be an extremely valuable nondestructive analytical tool and in many cases, the only method for performing specific analyses at high sensitivities... 

During the red giant phase of stellar evolution, free neutrons are generated by reactions such as C(a,n) and Ne(a,n) Mg. (The (ot,n) notation signifies a nuclear reaction where an alpha particle combines with the first nucleus and a neutron is ejected to form the second nucleus.) The neutrons, having no charge, can interact with nuclei of any mass at the existing temperatures and can in principle build up the elements to Bi, the heaviest stable element. The steady source of neutrons in the interiors of stable, evolved stars produces what is known as the "s process," the buildup of heavy elements by the slow interaction with a low flux of neutrons. The more rapid "r process" occurs in... 

Because the path of the s process is blocked by isotopes that undergo rapid beta decay, it cannot produce neutron-rich isotopes or elements beyond Bi, the heaviest stable element. These elements can be created by the r process, which is believed to occur in cataclysmic stellar explosions such as supemovae. In the r process the neutron flux is so high that the interaction hme between nuclei and neutrons is shorter that the beta decay lifetime of the isotopes of interest. The s process chain stops at the first unstable isotope of an element because there is time for the isotope to decay, forming a new element. In the r process, the reaction rate with neutrons is shorter than beta decay times and very neutron-rich and highly unstable isotopes are created that ultimately beta decay to form stable elements. The paths of the r process are shown in Fig. 2-3. The r process can produce neutron-rich isotopes such as Xe and Xe that cannot be reached in the s process chain (Fig. 2-3). 

In addition to stable elements, radioactive elements are also produced in stars. The unstable but relatively long-lived isotopes °K, Th, and make up the internal heat source that drives volcanic activity and processes related to internal convection in the terrestrial planets. The short-lived transuranium elements such as Rn and Ra that are found on the Earth are all products of U and Th decay. 

Except for the elements at the ends of the rows, each transition metal can exist in several different oxidation states. The oxidation states displayed by the 3d transition metals are shown in Table 20-1. The most important oxidation states are highlighted in the table. The most common oxidation state for the 3d transition metals is +2, known for all the elements except Sc. Chromium, iron, and cobalt are also stable in the +3 oxidation state, and for vanadium and manganese the -H4 oxidation state is stable. Elements from scandium to manganese have a particularly stable oxidation state corresponding to the loss of ah the valence electrons configuration). 

The half-lives of the elements vary widely, as shown in Table 3.2. Some isotopes, nitrogen-14 for example, are stable and experience no natural radioactive decay. However, bombarding even a stable element with energetic alpha rays can cause transmutation. Rutherford discovered the proton when he created hydrogen from a stable isotope of nitrogen. 

Where c, is the concentration of an element measured at the surface, Cbt is the concentration of a stable element due to batch melting and a, is the enrichment factor due to transport. The concentrations in the melt are given by the batch melting equation. 

As with donor particles, in order to resolve the posed problem it is initially necessary to prove experimentally a rigorous validity relationships derived in above domain of parameters (pressure and temperature) based on substantially wide number of experimental results. It is known that when preparing such experiments it is recommended to avoid various reefs which may provoke an experimentalist to take wrong assumptions for real, or to hide from a theorist, for example, simple functions in relationships analysed. Pioneering experiments conducted with acceptors involved such active particles as molecular oxygen which on the one hand possesses strong acceptor properties, and on the other is a fairly widespread and chemically sufficiently stable element. 

The brittle, silvery, shiny metal was long considered the last stable element of the Periodic Table. In 2003 it was unmasked as an extremely weak alpha emitter (half-life 20 billion years). Like thulium, there is only one isotope. Bismuth alloys have low melting points (fuses, fire sprinklers). As an additive in tiny amounts, it imparts special properties on a range of metals. Applied in electronics and optoelectronics. The oxichloride (BiOCl) gives rise to pearlescent pigments (cosmetics). As bismuth is practically nontoxic, its compounds have medical applications. The basic oxide neutralizes stomach acids. A multitalented element. Crystallizes with an impressive layering effect (see right). 

The position on the periodic chart under lead would be filled by an element of atomic number 114. No such element is yet known, but scientists theorize that this would be a very stable element if it could be found or created, and it might have some very important uses. This much-sought element is referred to as i eka-lead, using the naming system Mendeleyev used for undiscovered elements in the original periodic chart. 

No element is ever destroyed by use. The radioactive ones decay, but stable elements may be used over and over. The nitrogen cycle shows how the nitrogen atoms in your body and the ones in the air have been combining and recombining for millions of years. 

The experiments performed by Amdurer [847] were not intended to study chemical speciation or cycling of natural elements in the ecosystem. To do this, the tracers must be fully equilibrated with all of the reactive (i.e., nonmatrix) phases of the stable elements. This equilibration may require a time... 

Papadopoulu, C., G.D. Kanias, and E.M. Kassimati. 1976. Stable elements of radioecological importance in certain echinoderm species. Mar. Pollut. Bull. 7 143-144. 

Papadopoulu, C. and E.M. Kassimati. 1977. Stable elements in skeletal formations of fish species from Greek waters. Thai. Jugoslavia 13 187-192. 

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