Atomic properties noble gases

Tie chemical properties of an element depend primarily on its number of valence electrons in its atoms. The noble gas elements, for example, all have similar chemical properties because the outermost energy levels of their atoms are completely filled. The chemical properties of ions also depend on the number of valence electrons. Any ion with a complete outermost energy level will have chemical properties similar to those of the noble gas elements. The fluoride ion (F ), for example, has a total of ten electrons, eight of which fill its outermost energy level. F has chemical properties, therefore, similar to those of the noble gas neon. 

The noble gas core represents all electrons contained in an atom of noble gas. The similar chemical properties of the elements in the 5A group is attibuted to the similar arrangement of the outer shell electrons of all the members of the group ns np. The outermost shell is vital for determining the chemical properties of the elements and is called the valence shell. Similar regularities appear in the other groups of the periodic table. 

Some molecules have more than one valid Lewis structure, a property called resonance. Although Lewis structures in which the atoms have noble gas electron configurations correctly describe most molecules, there are some notable exceptions, including O2, NO, NO2, and the molecules that contain Be and B. 

Superatoms are atomic clusters which mimic the behavior of an atom in its elemental state. For example Aly, AI13, and Alj4 exhibit the properties of a germanium atom, a halogen atom, a noble gas atom and an alkaline earth metal atom, respectively. Since Aly is a multivalent superatom it can give rise to stable compounds like AlyC" and AlvO" (Fig. 10) which in turn show the characteristics of SiC and CO, respectively. 

The electron configuration is the orbital description of the locations of the electrons in an unexcited atom. Using principles of physics, chemists can predict how atoms will react based upon the electron configuration. They can predict properties such as stability, boiling point, and conductivity. Typically, only the outermost electron shells matter in chemistry, so we truncate the inner electron shell notation by replacing the long-hand orbital description with the symbol for a noble gas in brackets. This method of notation vastly simplifies the description for large molecules. 

Hexaammineplatinum(IV), effective atomic number of noble gas, 7 590t Hexaaquachromium(III) ion, 6 533 Hexaaquamolybdenum(III) ion, 27 26-27 Hexaarylbiimidazolyl (HABI), piezochromic materials, 6 608 Hexabis(benzylthiomethyl)benzene, 24 180 Hexaborane(lO), physical properties of, 4 184t Hexaborane(12), 4 186 Hexabromocyclododecane, 22 467-468 formulations of, 22 460t physical properties of, 4 355t Hexabromocyclohexane, 3 602 Hexachlorobenzene, 3 602 Antoine constants, 6 215t physical and thermodynamic properties, 6 214t... 

It was discovered, however, that the spherical aromaticity of the icosahedral fullerenes C20, Cjq and CgQ depends on the filling of the Jt-sheUs with electrons [107]. As pointed out in Section 14.3.1 no distortion of the cage structure is expected in these fullerenes if their shells are fully filled. Closed-shell situations are realized if the fullerene contains 2(N -1-1) Jt electrons. This is closely related to the stable noble-gas configuration of atoms or atomic ions [108]. In this case the electron distribution is spherical and all angular momenta are symmetrically distributed. Correlation of the aromatic character determined by the magnetic properties is shown in Table 14.3. 

The question then arises what is a heavy atom Br and I can be considered as heavy atoms in organic molecules, but Cl is a borderline case. Most metals qualify as heavy atoms and the photophysical properties of metal complexes are related to this increased spin-orbit coupling. Some noble gas heavy atoms like Xe show important external heavy atom effects. 

Mercury, with filled 5d and 6s subshells, also has the pseudo noble gas configuration. In the gas phase, Hg exists as a monatomic molecule. From Fig. 2.4.1, Hg has an I value similar to those of noble gases it occupies a maximum position in the h curve. The interaction between mercury atoms is of the van der Waals type. Hence, Hg and Au have some notably different properties ... 

If the elements 112 and 114 have a noble-gas like character [62], then, in a fictitious solid state, they would form non conducting colorless crystals. A physisorptive type of adsorption may occur and their adsorption properties, for example on quartz, can be calculated with this method [61], see Table 3. For physisorbed noble gas atoms a roughly uniform distance to different surfaces of about 2.47 0.2 A was deduced from experimental results [63]. 

Due to the expected high volatility of elements with atomic numbers 112 to 118 in the elemental state [104], see also Chapters 2 and 6, gas phase chemical studies will play an important role in investigating the chemical properties of the newly discovered superheavy elements. An interesting question is, if e.g. elements 112 and 114 are indeed relatively inert gases (similar to a noble gas) [105] due to closed s2 and p /22 shells, respectively, or if they retain some metallic character and are thus adsorbed quite well on certain metal surfaces, see Chapter 6, Part II, Section 3.2. Extrapolations by B. Eichler et al. [106] point to Pd or Cu as ideal surfaces for the adsorption of superheavy elements. 

The bulk properties of macroscopic crystals cannot be affected drastically by the difference which exists between the structure of the interior and that of a surface film which is approximately 10,000 atoms deep. However, even for macroscopic crystals, rate phenomena such as modification changes which are initiated within the surface are likely to be influenced by the environment, which would include molecules which are conventionally described as physically adsorbed. Apparently it is not generally understood that even the presence of a noble gas can affect the chemical reactivity of solids. Brunauer (3) explained that in principle physical adsorption of molecules should affect the solid in the same manner as chemisorption. As action and reaction are equal, chemisorption may have a stronger effect on both the solid and the adsorbed molecule. 

The poorly defined concept of the metal-metal bond9- sometimes makes it difficult to distinguish between real and false metal-metal bonds. Many metal-metal bonds are only supposed to exist because of intermetallic distances corresponding to those in the metallic state or because magnetic properties or the noble gas rule demand an interaction between neighbouring metal atoms. 

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