Sulfur hexafluoride molecules

A sulfur hexafluoride molecule, SF6, has six atoms attached to the central S atom and no lone pairs on that atom (8). According to the VSEPR model, the electron arrangement is octahedral, with four pairs at the corners of a square on the equator and the remaining two pairs above and below the plane of the square (see Fig. 3.2). An F atom is attached to each electron pair, and so the molecule is predicted to be octahedral. All its bond angles are either 90° or 180°, and all the F atoms are equivalent. 

He, because a helium atom is much smaller than a sulfur hexafluoride molecule, which better approximates the first tenet of the kinetic molecular theory of gases. 

C) This statement is correct. The sulfur hexafluoride molecule has a much larger volume than the other molecules and is much more likely to experience molecular attractions than the other two molecules. These two factors will make this molecule most likely to deviate from the key postulates in the kinetic-molecular theory (size of the molecule is negligible and molecular attractions are negligible). 

The Group VIA elements below oxygen form some covalent compounds of the ABg type by sharing their six valence electrons with six other atoms. Sulfur hexafluoride, SFg (mp — 51 °C), an unreactive gas, is an example. Sulfur hexafluoride molecules are nonpolar octahedral molecules. The hexafluorophosphate ion, PFg, is an example of a polyatomic ion of the type AB. ... 

Intermolecular forces involving sulfur hexafluoride molecules have been discussed in several papers (91, 121, 122, 194, 350, 296). Other studies include (a) molecular volume (254), (b) stopping of alpha particles (16,117), (c) transfer of energy by collision (205), (d) mutual diffusion of H2 and SF6 (291), (e) mutual solubilities of gases, including SF , in water (197), (f) salting out of dissolved gases (219), (g) compressibility (193) (h) Faraday effect (161), (i) adsorption on dry lyophilized proteins (14), (j) effect of pressure on electronic transitions (231), (k) thermal relaxation of vibrational states (232), (1) ultraviolet spectrum (295), (m) solubility in a liquid fluorocarbon (280). 

The largest class of molecules to violate the octet rule consists of species in which the central atom is surrounded by more than four pairs of valence electrons. Typical molecules of this type are phosphorus pentachloride, PC15, and sulfur hexafluoride, SF6. The Lewis structures of these molecules are... 

A molecule with a steric number of 6 requires six hybrid orbitals arranged in octahedral geometry. In Chapter 9, sulfur hexafluoride appears as the primary example of a molecule with a steric number of 6 (Figure ). Six equivalent orbitals for sulfur can be constmcted for the inner sulfur atom by combining the 3. S, the three 3 p,... 

Analysis of the halohydrocarbons, halocarbons, and sulfur hexafluoride is usually achieved by gas chromatography that is equipped with an electron capture detector. Complex metal anions, such as cobalt hexacyanide, are used as nonradioactive tracers in reservoir studies. The cobalt in the tracer compound must be in the complex anion portion of the molecule, because cationic cobalt tends to react with materials in the reservoir, leading to inaccurate analytic information [1226]. 

At a constant temperature, lighter gas molecules diffuse faster than heavier molecules. The reverse is true which might make one conclude that Balloon C is filled with sulfur hexafluoride. 

The results (electrostatic-fit charges based on Hartree-Fock 6-3IG wavefunctions) are ambiguous. Relative to dimethylsulfide as a normal-valent standard , the sulfur in oxygen loses about half an electron, and the sulfur in dimethylsulfone loses 1.7 electrons. This would seem to suggest that dimethylsulfoxide is halfway to being a zwitterion, but that dimethylsulfone is most of the way. Charges on sulfur in sulfur tetrafluoride and sulfur hexafluoride (relative to sulfur difluoride) show more modest effects, in particular for the latter. Overall, it appears that hypervalent molecules possess significant ionic character. 

As was true in the case of five charge clouds, different shapes are possible for molecules having atoms with six charge clouds, depending on whether the clouds are of bonding or nonbonding electrons. Sulfur hexafluoride, for example, has all six positions around sulfur occupied by fluorine atoms ... 

This also proves an earlier conclusion on hyperconjugation in an 0CH20 fragment of the 1,3-dioxolane cation radical this conclusion was based on mass spectrometry (To-dres, Kukovitskii et al. 1981). As calculated, the carbon-hydrogen bonds corresponding to 0CH20 in the radical cation are weaker than those in the neutral molecule. For this reason, this site exhibits a maximal probability that deprotonation will result in the formation of the 2-yl radical (Belevskii et al. 1998). In experiments, photoirradiation of 1,3-dioxolane solutions in sulfur hexafluoride at 77 K really leads to formation of the cation radical of 1,3-dioxolane and the l,3-dioxolan-2-yl radical as a result of deprotonation. Consecutive ring... 

Sulfur hexafluoride sublimes at -64 °C to produce a dense gas (6.14 g L-1). Under a pressure of 2 atm, the melting point is -51 °C. The molecule has the expected octahedral structure and a dipole moment of zero. The compound is so inert that it is used as a gaseous insulator, and rats allowed to breathe a mixture of SF6 and oxygen show no ill effects after several hours of exposure. This inertness is a result of the molecule having no vacant bonding site or unshared electron pairs on sulfur to initiate a reaction and the fact that six fluorine atoms shield the sulfur atom from attack. Consequently, there is no low-energy pathway for reactions to occur, and the compound is inert even though many reactions are thermodynamically favored. 

A typical problem of interest at Los Alamos is the solution of the infrared multiple photon excitation dynamics of sulfur hexafluoride. This very problem has been quite popular in the literature in the past few years. (7) The solution of this problem is modeled by a molecular Hamiltonian which explicitly treats the asymmetric stretch ladder of the molecule coupled implicitly to the other molecular degrees of freedom. (See Fig. 12.) We consider the the first seven vibrational states of the mode of SF (6v ) the octahedral symmetry of the SF molecule makes these vibrational levels degenerate, and coupling between vibrational and rotational motion splits these degeneracies slightly. Furthermore, there is a rotational manifold of states associated with each vibrational level. Even to describe the zeroth-order level states of this molecule is itself a fairly complicated problem. Now if we were to include collisions in our model of multiple photon excitation of SF, e wou d have to solve a matrix Bloch equation with a minimum of 84 x 84 elements. Clearly such a problem is beyond our current abilities, so in fact we neglect collisional effects in order to stay with a Schrodinger picture of the excitation dynamics. 

Let us consider now an octahedral AX6 molecule, e g., sulfur hexafluoride, SF6, which has the symmetry of the regular octahedron Oh. Substitution of an X ligand by a B ligand results in an AX5B... 

Examples of molecules in which the central atom contains an expanded octet are the phosphorus pentahalides and sulfur hexafluoride. 

The molecule sulfur hexafluoride SF6 exemplifies one of the most common types of d orbital hybridization. The six bonds in this octahedrally-coordinated molecule are derived from mixing six atomic orbitals into a hybrid set. The easiest way to understand how these come about is to imagine that the molecule is made by combining an imaginary S6+ ion (which we refer to as the S(VI) valence state) with six F ions to form the neutral molecule. These now-empty 3s and 3p orbitals then mix with two 3d orbitals to form the sp3d2 hybrids. 

FIG. 15-5. Molecules of silicon tetrafluoride, phosphorus penta-fluoride, and sulfur hexafluoride, three very volatile substances. 

Oxygen molecules have an average speed of about 480 m/s at room temperature. At the same temperature, what is the average speed of molecules of sulfur hexafluoride, SFe ... 

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