Properties of Elements

One of the early triumphs of the Mendeleef Periodic Table was the prediction of the properties of elements which were then unknown. Fifteen years before the discovery of germanium in 1886, Mendeleef had predicted that the element which he called ekasilicon would be discovered, and he had also correctly predicted many of its properties. In Table 1.8 his predicted properties are compared with the corresponding properties actually found for germanium. 

One of the most significant sources of change in isotope ratios is caused by the small mass differences between isotopes and their effects on the physical properties of elements and compounds. For example, ordinary water (mostly Ej O) has a lower density, lower boiling point, and higher vapor pressure than does heavy water (mostly H2 0). Other major changes can occur through exchange processes. Such physical and kinetic differences lead to natural local fractionation of isotopes. Artificial fractionation (enrichment or depletion) of uranium isotopes is the basis for construction of atomic bombs, nuclear power reactors, and depleted uranium weapons. 

Study of the chemical properties of element 104 has confirmed that it is indeed homologous to hafnium as demanded by its position in the Periodic Table (20). Chemical studies have been made for element 105, showing some similarity to tantalum (25) no chemical studies have been made for elements 106—109. Such studies are very difficult because the longest-Hved isotope of 104 ( 104) has a half-Hfe of only about 1 min, of 105 ( 105) a half-Hfe of about 40 s, of 106 ( 106) a half-Hfe of about 1 s, and of elements 107—109 half-Hves in the range of milliseconds. 

E. A. Brandes and R. E. Flint, Manganese Phase Diagrams, The Manganese Centre, Paris, 1980 L. B. Pankratz, Thermodynamic Properties of Elements and Oxides, Bull. 672, U.S. Bureau of Mines, Washington, D.C., 1982. 

Thermodynamic. The thermodynamic properties of elemental plutonium have been reviewed (35,40,41,43—46). Thermodynamic properties of sohd and Hquid Pu, and of the transitions between the known phases, are given in Table 5. There are inconsistencies among some of the vapor pressure measurements of Hquid Pu (40,41,43,44). 

Thermodynamic. Thermodynamic properties of Pu metal, gaseous species, and the aqueous ions at 298 K are given in Table 8. Thermodynamic properties of elemental Pu (44), of alloys (68), and of the gaseous ions Pu", PuO", PuO" 27 PuO 2 (67) have been reviewed, as have those of aqueous ions (64), oxides (69), haUdes (70), hydrides (71), and most other compounds (65). 

An extensive compilation of the properties of compound semiconductors may be found in the Landolt-Bn mstein reference books (13,14). Various subvolumes in the series cover the properties of elemental. III—V, II—V, and other less common semiconductors. Information may also be found concerning semiconductor technology. Another useful source of information is the EMIS data review series (15). These books describe the properties and technology of GaAs, HgCdTe, InP, AlGaAs, InGaAs, and the III—V nitride compounds. 

The physical properties of elemental sulfur can be modified by its reaction with various organic and inorganic compounds. Many of the resulting sulfur products tend to have properties similar to paving asphalt (49,50). 

The physical properties of elemental boron are significantly affected by purity and crystal form. In addition to being an amorphous powder, boron has four crystalline forms a-rhombohedral, P-rhombohedral, a-tetragonal, and -tetragonal. The a-rhombohedral form has mp 2180°C, sublimes at approximately 3650°C, and has a density of 2.45 g/mL. Amorphous boron, by comparison, has mp 2300°C, sublimes at approximately 2550°C, and has a density of 2.35 g/mL. 

The physical and thermodynamic properties of elemental hydrogen and deuterium and of their respective oxides illustrate the effect of isotopic mass differences. 

Table 5.2 Electrical properties of elemental and compound semiconductors...

The chemical and electronic properties of elements at the interfaces between very thin films and bulk substrates are important in several technological areas, particularly microelectronics, sensors, catalysis, metal protection, and solar cells. To study conditions at an interface, depth profiling by ion bombardment is inadvisable, because both composition and chemical state can be altered by interaction with energetic positive ions. The normal procedure is, therefore, to start with a clean or other well-characterized substrate and deposit the thin film on to it slowly at a chosen temperature while XPS is used to monitor the composition and chemical state by recording selected characteristic spectra. The procedure continues until no further spectral changes occur, as a function of film thickness, of time elapsed since deposition, or of changes in substrate temperature. 

B. Fricke, Superheavy elements, Structure and Bonding 21, 89 (1975). A full account of the predicted stabilities and chemical properties of elements with atomic numbers in the range Z = 104- 184. 

Figure 21.1 Trends in some properties of elements of Groups 4 and 14.

Periodic function A physical or chemical property of elements that varies periodically with atomic number, 152 Periodic Table An arrangement of the elements in rows and columns according to atomic numbers such that elements with similar chemical properties foil in the same column,... 

There are similar, but smaller, trends in the properties of elements in a column (a family) of the periodic table. Though the elements in a family display similar chemistry, there are important and interesting differences as well. Many of these differences are explainable in terms of atomic size. 

To understand how the electron has been applied to explanations of the periodic table we must start with the discovery of the periodic system itself. The Russian chemist Dimitri Mendeleev announced in 1869 that the properties of elements arranged in order of increasing atomic weight appeared to repeat after certain definite intervals. Yet even as this discovery became increasingly well established, Mendeleev remained strongly opposed to any attempt to reduce or explain the periodicity in terms of atomic structure. He resisted the notion of any form of primary matter, which was actively discussed by his contemporaries, and opposed... 

We need insight to think like a chemist. Chemical insight means that, when we look at an everyday object or a sample of a chemical, we can imagine the atoms that make it up. Not only that, we need to be able to plunge, in our mind s eye, deep into the center of matter and imagine the internal structure of atoms. To visualize this structure and how it relates to the chemical properties of elements, we need to understand the electronic structure of an atom, the description of how its electrons are arranged around the nucleus. 

We are now at the point where we can begin to use the periodic table as chemists and materials scientists do—to predict the properties of elements and see how they can be used to create the materials around us and to design new materials for tomorrow s technologies. 

The periodic table is a catalog of the elements, each with its own unique set of physical and chemical properties. Each element has a unique value for Z, the positive charge on its nucleus. The number of electrons possessed by a neutral atom of that element is also equal to Z. The different properties of elements arise from these variations in nuclear charges and numbers of electrons. 

By explicitly showing the relationship between the elements, Mendeleyev was able to predict the existence and properties of elements that had not yet been discovered. He theorized, for example, that an undiscovered element should fall between silicon and tin on the periodic table. In 1880, German chemist Clemens Winkler isolated a new element, which he named germanium, that had exactly the properties that Mendeleyev predicted. 

Read over the entire laboratory activity. Hypothesize which method you expect to be the best in confirming the known properties of Ca and K. The worst Hypothesize which method you expect to be the best in predicting the properties of elements 31-36. Record your hypothesis on page 46. 

Use the best predictive method (1 or 2) for each property to predict the properties of elements 31-36 in groups 3A-7A. Record the predicted values in Data Table 4. 

What unique property of elements 103 and greater would be most useful in placing them in the correct position in the periodic table ... 

Most solar cells rely upon the natural properties of element bb. 

The literature on the physical properties of elements and compounds is extensive, and reliable values for common materials can usually be found. The principal sources of physical property data are listed in the references at the end of this chapter. 

Some chemical properties of element 43. II. J. chem. Physics 7, 155... 

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