Parent elements

The rare earth elements (R) are those from atomic numbers 57-71, emanating as a particular series from the parent element lanthanum (atomic no. 57). The set of 14 elements from cerium (58) through lutetium (71) inclusive are commonly known as the lanthanoid (or lanthanide Ln) series. The rare earths form a bridge at the... 

As explained below, most melting models are highly sensitive to the D values chosen for the parent elements U and Th. For example, in the case of simple batch melting, it can be shown that the U- Pa fractionation will only depend on the partition coefficients for U as long as Dpa is essentially zero ... 

Different locations of parent elements. and Th are generally located in minor phases within host rocks. Due to different U/Th ratios in these phases, recoil from the two chains may be affected by different surrounding matrix characteristics or mineral sizes. Not only might the primary distribution of U and Th be different, but earlier weathering or alteration may also have redistributed U and Th. This is discussed further below. 

The recognition of element transformation allowed the idea of a series of elements forming sequentially from the decay of a parent element and led to the first published set of U-series in 1903 (Rutherford 1903) ... 

Secular Equilibrium—If a parent element has a very much longer half-life than the daughters (so there is not appreciable change in its amount in the time interval required for later products to attain equilibrium) then, after equilibrium is reached, equal numbers of atoms of all members of the series disintegrate in unit time. This condition is never exactly attained, but is essentially established in such a case as 226Ra and its transformation series to stable 206Pb. The half-life of 226Ra is about... 

This results in the transmutation of parent element X into daughter Y, which has an atomic number two less than X. The particular isotope of element Y which is formed is that with an atomic mass of four less than the original isotope of X. Note that, as in chemical reactions, these nuclear reactions must be numerically balanced on either side of the arrow. Many of the heavy elements in the three naturally occurring radioactive decay chains (see below) decay by a-emission. 

So, now (1913) one has a set of rules which characterize the daughter atom in terms of a knowledge of the parent element and the type of radioactive decay. The rules work they give rise to the concept of isotopes elements which correspond to different atomic weights but which are chemically identical. However, the rules are purely empirical no explanation exists for the rules as the matter now stands. Something is still missing in this story. 

Molecules based on nitrogen, the parent element of ammonia and the amines, and oxygen, the parent element of water, are key molecules of life. 

Listed as asphyxiants are the much more inert gases of argon, helium, hydrogen, neon, and nitrogen. Many elements are missing from this table, either because they are harmless or because they have not been measured. The values listed in table 6.6 are for the elements, but some of them have compounds that are much more toxic than the parent element. For instance, platinum metal is toxic at 1 mg/m, but soluble plahnum salts are toxic at 0.002 mg/m. ... 

Again, both mass and charge are conserved. Gamma emission often accompanies both alpha and beta decay, but because gamma emission does not change the parent element it is often emitted when writing nuclear reactions. 

One of the most important observations of atoms is the set of relationships between elements that belong to one of the series of radioactive decays. The parent elements of uranium, thorium and actinium decay through many intermediates to the stable element lead. The Nobel Prize in Chemistry for 1921 was awarded in 1922 to Frederick Soddy for his complete characterization of these processes. The story is beautifully told in his Nobel Lecture entitled The origins of the conception of isotopes (25). 

Radiometric age dating is a powerful chronological tool. It is based on the accumulation of the daughter nuclide produced by the decay of the parent isotope. If the decay rate is known, and if one can measure the amounts of parent element and daughter isotope, then it is... 

Consider a hypothetical system that has an initial abundance of a short-lived radionuclide Nr. This nuclide is present as a fixed fraction of the parent element and its abundance can be written as the ratio of the radionuclide to a stable reference isotope of the same element, Ns. When the short-lived nuclide has completely decayed to its daughter nuclide, D, we have ... 

The other is the ratio of the abundance of the reference isotope of the parent element to the abundance of the reference isotope of the daughter element ... 

In XPS, on the other hand, photoelectrons, which are emitted when the sample surface is irradiated with a beam of x-rays, are analyzed. The emitted photoelectrons have discrete binding energies that are dependent on both the identity of the parent element and its chemical environment in the surface. Therefore, both the concentration and the chemical state of an element in the surface can be determined. Two advantages of XPS are that the incident x-ray beam is practically harmless to the surface and it also does not induce charging effects, so that the surface chemistry of adhesives and other insulators can readily be investigated 171 ... 

Some use has been made of V ores in pyrot smokes (Ref 5). V is the parent element of the expl and energetic compds entered below. Metallic V is non-toxic (Refs 1,6,7,13,14,15, 16 18)... 

The periodic table is a great help in deciding whether a binary oxide is likely to form an acidic or basic solution in water. For main-group elements, it is usually sufficient to note whether the parent element of the compound is a metal or a nonmetal. Most soluble metal oxides are strong bases in water. Conversely, many nonmetal oxides react with water to give acids ... 

The nature of the binary hydride is related to the characteristics of the parent element (Fig. 14.8). Strongly electropositive metallic elements form ionic compounds with hydrogen in which the latter is present as a hydride ion, H, and has oxidation number —1. These ionic compounds are called saline hydrides (or saltlike hydrides ). They are formed by all members of the s block with the exception of beryllium and are made by heating the metal in hydrogen ... 

As a general rule, the properties of interhalogen compounds are intermediate between those of their parent elements. For example, IC1 is a red solid that melts near room temperature, and BrF is a brownish gas that condenses to a liquid near room temperature. All six possible diatomic interhalogen compounds are known, and all act as strong oxidizing agents in redox reactions. 

Figure 3.1 The product of a chemical reaction can be quite different from its "parent" elements, a) Sodium is a soft metal that is highly reactive with water, b) Chlorine is a toxic gas. c) The highly reactive sodium and dangerously toxic chlorine, when combined, create a perfectly harmless addition to any kitchen table salt.

But when sodium metal and chlorine gas react with one another, the product is neither flammable nor poisonous. The reaction of these two chemicals makes sodium chloride, or ordinary table salt. Even though table salt has sodium and chlorine atoms in it, its chemical properties are very different than the chemical properties of either of its parent elements. That is because the atoms of the two very different elements have formed a compound that is now held together by chemical bonds in an arrangement that gives the compound unique chemical properties. 

Component separation is often particularly prominent when one or more of the components present is in situ. There is no requirement that different components reside in different minerals indeed, it is often not known at all where the components reside. An in situ component will be sited wherever its parent element is, and this siting might be rather different from that of some other in situ component or a trapped component, as illustrated in Fig. 2.12. Radiogenic gases are common in situ components, and stepwise heating is frequently applied to resolving them from other components. 

---