Lanthanum general properties

Only limited information is available about actinium. It is known to be a silver metal with a melting point of 1,920°F (1,050°G) and a boiling point estimated to be about 5,800°F (3,200°C). The element has properties similar to those of lanthanum. Generally speaking, elements in the same column in the periodic table have similar properties. Few compounds of actinium have been produced. Neither the element nor its compounds have any important uses. 

It was not until 1859 that Bunsen first applied the spectrograph to analytical chemistry determinations, and this development proved useful in the case of the rare earths. The nature of the spectra of the various rare earths was not understood until well into the Twentieth century, so the analytical methods were empirical and not always dependable. The uncertainty was due to the fact that the transition elements also separated along with the rare earths in the fractionation process, and tended to complicate the various spectra obtained. As a result of these complications, the discovery of over 70 new rare earths was reported in the literature. Many of the new elements were based on spectra differences in the fractions obtained, and no one knew how many rare earths should exist. It was not until 1869 that Mendeleyev published his first periodic chart. Incidentally, in doing so, he had to leave a blank where scandium now occurs, and he predicted a new element would be found which would have the general properties now attributed to the rare earths. Shortly afterwards (1879) scandium was discovered, and its discovery greatly aided in the general acceptance of Mendeleyev s ideas. While the chart had a place for lanthanum, there was no place in his chart for the other rare earths, since they also seemed to fall in the space reserved for lanthanum. The early chemists seemed to think they were discovering a new type of element with properties very similar to the properties which we now ascribe to isotopes, and some even speculated that these other rare earths were different modifications of lanthanum. 

Table 1. General properties of ions of scandium, yttrium, lanthanum and lanthanoids. 

ZnO photocatalyst can also be coupled with other materials in order to improve its chemical and physical properties [183] and photocatalytic activity [184]. Nanosized ZnO was immobilized on aluminum foil for the degradation of phenol [185]. Lanthanum and ZnO were combined to degrade 2,4,6-trichlorophenol [186]. Compared with Ti02 nanomaterial, ZnO nanomaterial generally absorbs a significant amount of the solar spectrum in the visible range therefore, ZnO nanomaterials were combined with Ti02 nanomaterials used as a photocatalyst [187]. 

The formation and properties of the lanthanide complex species can be best understood by summarizing first some of the pertinent general characteristics of these elements. In their ground states, the lanthanide atoms have the characteristic valence-shell electronic configurations 4/"5 d 6 or 4 / + 6 where n = 0 for lanthanum and 14 for lutetium, overlying the closed-shell xenon arrangement. The atoms are large and readily oxidized. In both aqueous or nonaqueous systems and the solid state, oxidation... 

For the two common lanthanides lanthanum and neodymium that there are no quality heat capacity measurements available between 20 and 298 K and the selected entropy values at 298 K are therefore little more than educated guesses. Further measurements are also required on alpha cerium between 20 and 96 K in order to obtain a precision value for the entropy at 298 K. What is woiryingly being shown up by these reviews is that for many of these elements, selected values in a particular region are generally based on only one set of measurements since other measurements differ so significantly that they cannot be considered. It is possible that measurements on the pure metals will become fewer and fewer as there is a concentration oti commercially exploiting the many extraordinary properties of lanthanide compounds. 

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