Natural States of the Elements

As we have noted, the matter around us consists mainly of mixtures. Most often these mixtures contain compounds, in which atoms from different elements are bound together. Most elements are quite reactive their atoms tend to combine with those of other elements to form compounds quite readily. As a result, we do not often find elements in nature in pure form—uncombined with other elements. However, there are notable exceptions. The gold nuggets found at Sutter s Mill in California that launched the Gold Rush in 1849 are virtually pure elemental gold. Platinum and silver are also often found in nearly pure form. 

A gold nugget weighing 13 lb, 7 oz, which came to be called Tom s Baby, was found by Tom Grove near Breckenridge, Colorado, on July 23, 1887. 

Because the atoms of these Group 8 elements do not combine readily with those of other elements, we call them the noble gases. 

For example, helium gas is found in uncombined form in underground deposits with natural gas. 

Argon gas consists of a collection of separate argon atoms. 

As we have noted, the matter around us consists mainly of mixtures. Most often these mixtures contain compounds, in which atoms from different elements are bound together. Most elements are quite reactive their atoms tend to combine with those of other elements to form compounds. Thus 

Recall that a molecule is a collection of atoms that behaves as a unit. Molecules are always electrically neutral (zero charge). 

silver, and platinum are members of a class of metals called noble metals because they are relatively unreactive. (The term noble implies a class set apart.) 

Other elements that appear in nature in the uncombined state are the elements in Group 8 helium, neon, argon, krypton, xenon, and radon. Because the atoms of these elements do not combine readily with those of other elements, we call them the noble gases. For example, helium gas is found in uncombined form in underground deposits with natural gas. 

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Introduction to the Periodic Table Natural States of the Elements Ions... 

Analysis of the peaks provides qualitative information, on the chemical nature and state of the elements, and quantitative information, regarding the relative numbers of atoms of each type present on the surface. 

Figure 22-1 Major natural sources of the elements. The soluble halide salts are found in oceans, salt lakes, brine wells, and solid deposits. Most helium is obtained from wells in the United States and Russia. Most of the other noble gases are obtained from air.

As shown by Figure 1, a bewildering number of different materials have been added to THF in an effort to induce its polymerization. Figure 1 shows just the elements in these materials and the position of those elements in the Periodic Chart. The nature of the compounds and especially the oxidation state of the elements in the compounds are very important if a given material is to be an initiator, but as we shall see, the kinds of active compounds that are useful and the manner in which active compounds can be used is related to the position in the Periodic Chart of the principal elements of which the compound is comprised. 

The most stable allotrope is orthorhombic sulfur (the a-form and standard state of the element) and it occurs naturally as large yellow crystals in volcanic areas. At 367.2 K, the ot-form transforms reversibly into monoclinic sulfur (j3-form). Both the a- and jB-forms contain Sg rings the density of the a-form is 2.07gcm , compared with... 

X-ray emission spectra are sufficiently sensitive to changes in the density of electron states to provide useful Information in studies of the nature of chemical bonding. The relationships between the x-ray emission spectra and the state of the elements in compounds and alloys (and, consequently, the physical properties of matter) have already been established. Local x-ray spectroscopy can be used to tackle many special cases. The microanalyzer (MS-46) used in these investigations is capable of dealing with the emission spectra of elements rating from boron to uranium. The analysis can be limited to a region of 1 n diameter. 

This chapter deals with the periodicity of the valencies and oxidation states of the elements. An overview of chemical bonding is included to aid in the understanding of the periodicities of the enthalpies of atomization of the elements, and the nature and properties of their fluorides and oxides, which are the subjects of Chapters 6 and 7. 

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