F Physical Properties of the Elements

A Scientific Notation and Experimental Error A.2 B SI Units, Unit Conversions, Physics for General Chemistry A.9 C Mathematics for General Chemistry A.21 D Standard Chemical Thermodynamic Properties A.37 E Standard Reaction Potentials at 25°C A.45 F Physical Properties of the Elements A.47 G Solutions to the Odd-Numbered Problems A.57... 

Of the predominantly nonmetallic elements, seven are solids under ordinary atmospheric conditions (B, C, Si, P, S, Se, and I), only one is a liquid (Br), and the remainder are gases (H, N, 0, F, Cl, He, Ne, A, Kr, and Xe). The physical properties of these elements present far more striking contrasts than do those of the metals. Thus, among the nonmetals one encounters the extremely volatile helium, which boils at -267°C (i.e., just 5°C above absolute zero), and the nonvolatile element carbon, which melts at about 3500°C. Similarly, the densities and other physical properties of these elements differ tremendously, as is made more evident by an inspection of a table of physical properties of the elements. 

Table 8.1 lists some key physical properties of the elements of the first transition series, taken mostly from Appendix F. The general trends in all of these properties can be understood by recalling that nuclear charge also increases across a period as electrons are being added to the same subshell, in this case, the d shell. The first and second ionization energies tend to increase across the period, but not smoothly. The energies of the 4s and 3d orbitals are so close to one another that the electron configurations of the neutral atoms and their ions are not easily predicted from the simplest model of atomic structure. 

While complete X-ray analysis will establish the structure in the solid state, it is useful to have NMR data on the solution state that illustrate the increase of the coordination number of silicon. It would seem that NMR spectroscopy of nuclei participating directly in donor-acceptor interaction is especially important in investigating silicon compounds with an expanded coordination sphere. This requires the use of Si NMR spectroscopy since the electron shell of the silicon atom, the bond angles and lenghts are strongly affected upon complexation. Valuable information could also be obtained with by " N, N, 0, F NMR data since these elements act as donors. Chemical shifts of nuclei other than hydrogen are determined by various factors and not yet understood well anough to provide easily applied correlations of other physical properties of the molecules. 

It is not necessary to learn the numerical values of the various physical properties, but the trends that they follow from left to right and from the top to the bottom of the Periodic Table are important. Thus, it is useful information that with the exception of H and He, fluorine, F (64 pm), is the smallest element and potassium, K (227 pm) is the largest element in the first 18 elements of the Periodic Table. These three physical properties are clearly determined by the electron configurations of the elements and their positions in the Periodic Table. It is just this combination of these three physical properties that is responsible for the chemical properties of the elements. 

Hampel, E. F., ed., The Encyclopedia of the Chemical Elements, Reinhold, New York. Especially good on occurrence, refinement, uses and physical properties of the individual elements. 

Additional electrons can fall into either of the d, f, or s orbitals, depending on which has the lowest energy requirement. This causes some fluctuation in the chemical and physical properties of the actinide elements. 

OCEAN WATER. An electrolyte solution containing minor amounts of nonelectrolytes and composed predominantly of dissolved chemical species of fourteen elements O, H, Cl, Na. Mg, S, Ca, K, Bl, C, Sr, B, Si, and F (Table 1). The minor elements, those that occur in concentrations of less than 1 ppm by v/eight. although unimportant quantitatively in determining the physical properties of sea water, are reactive and are important in organic and biochemical reactions in the oceans. 

Organic constituents that may be found in ppb levels in WP/F smoke include methane, ethylene, carbonyl sulfide, acetylene, 1,4-dicyanobenzene, 1,3-dicyanobenzene, 1,2-dicyanobenzene, acetonitrile, and acrylonitrile (Tolle et al. 1988). Since white phosphorus contains boron, silicon, calcium, aluminum, iron, and arsenic in excess of 10 ppm as impurities (Berkowitz et al. 1981), WP/F smoke also contains these elements and possibly their oxidation products. The physical properties of a few major compounds that may be important for determining the fate of WP/F smoke in the environment are given in Table 3-3. 

Very little is known about the physical and chemical properties of californium. Its melting point has been found to be 1,652°F (900°C) and its density, 15.1 grams per cubic centimeter, about 15 times that of water. It is also very radioactive. One microgram (millionth of a gram) of the element emits about three million neutrons per second. 

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