Fluorine atomic radius

It would be of practical importance to know how close two molecules can be to each other. We will not entertain this question too seriously, though, because this problem cannot have an elegant solution it depends on the direction of the approach and the atoms involved, as well as how strongly the two molecules collide. Searching for the effective radii of atoms would be nonsense, if the valence repulsion were not a sort of soft wall or if the atom sizes were very sensitive to molecular details. Fortunately, it turns out that an atom, despite different roles played in molecules, can be characterized by its approximate radius, called the van der Waals radius. The radius may be determined in a naive but quite effective way. For example, we may approach two HF molecules like that H-F...F-H, axially with the fluorine atoms heading on, then find the distance Rff which the interaction energy is equal to, say, 5 kcals/mol. The proposed fluorine atom radius would be A similar procedure may be repeated with... 

For halides the cation should have a charge of 2+ rather than 4+ for tetrahedral coordination. The only fluoride compound capable of containing two-coordinate F and four-coordinate cations is Bep2. For ZrF, the radius ratio rule predicts that Zr" " is eight-coordinate if all fluorine atoms are two - c o o rdinate. 

Assume that the nucleus of the fluorine atom is a sphere with a radius of 5 X 10-13 cm. Calculate the density of matter in the fluorine nucleus. 

Chemically they are extremely inert, being much more un-reactive even than the fluoroacetates. The inertness of the fluorocarbons and their nearly perfect physical properties arise from the strength of the F—C linkage and from their compact structure. The effective atomic radius of covalently bound fluorine is 0-64 A., which although greater than hydrogen (0-30) is smaller than other elements, e.g. Cl 0-99 A., Br 1-14 A. 

Whereas the van der Waals radius of the fluorine atom is the smallest one after that of hydrogen, its volume is actually closer to that of oxygen (Table 1.16). Note that if the volume is an intrinsic property, steric effects are dependent on the observed phenomena. They frequently appear in dynamic processes. This allows comparison of steric parameters of various groups, fluorinated or not. These parameters show that the CF3 group is at least as bulky as an isopropyl or isobutyl group (Table 1.17). These data are confirmed by the values of the rotation, or of inversion barriers, of fluorinated diphenyl-type compounds (Figure 1.6). 

The weakness of the covalent bond in dilithium is understandable in terms of the low effective nuclear charge, which allows the 2s orbital to be very diffuse. The addition of an electron to the lithium atom is exothermic only to the extent of 59.8 kJ mol-1, which indicates the weakness of the attraction for the extra electron. By comparison, the exother-micity of electron attachment to the fluorine atom is 333 kJ mol-1. The diffuseness of the 2s orbital of lithium is indicated by the large bond length (267 pm) in the dilithium molecule. The metal exists in the form of a body-centred cubic lattice in which the radius of the lithium atoms is 152 pm again a very high value, indicative of the low cohesiveness of the metallic structure. The metallic lattice is preferred to the diatomic molecule as the more stable state of lithium. 

Some general chemistry textbooks say that if a fluorine atom, Z = 9, gams an electron, it will become a fluoride ion with ten electrons that cannot be bound as tightly (because of electron-electron repulsion) as the nine of the neutral atom, so the radius of the fluoride ion (119 pm) is much greater than the radius of the neutral fluorine atom (71 pm). Discuss and criticize. 

Arrange the elements in the following sets in order of decreasing atomic radius (a) lithium, carbon, fluorine (b) scandium, vanadium, iron (c) iron, ruthenium, osmium (d) iodine, bromine, chlorine. 

All of these hexafluorides are dimorphic, with a high-temperature, cubic form and an orthorhombic form, stable below the transition temperature (92). The cubic form corresponds to a body-centered arrangement of the spherical units, with very high thermal disorder of the molecules in the lattice, leading to a better approximation to a sphere. Recently, the structures of the cubic forms of molybdenum (93) and tungsten (94) hexafluorides have been studied using neutron powder data, with the profile-refinement method and Kubic Harmonic analysis. In both compounds the fluorine density is nonuniformly distributed in a spherical shell of radius equal to the M—F distance. Thus, rotation is not completely free, and there is some preferential orientation of fluorine atoms along the axial directions. The M—F distances are the same as in the gas phase and in the orthorhombic form. 

PCTFE has better mechanical properties than PTFE because the presence of the chlorine atom in the molecule promotes the attractive forces between molecular chains. It also exhibits greater hardness, tensile strength, and considerably higher resistance to cold flow than PTFE. Since the chlorine atom has a greater atomic radius than fluorine, it hinders the close packing possible in PTFE, which results in a lower melting point and reduced propensity of the polymer to crystallize.7 The chlorine atom present in ECTFE, a copolymer of ethylene and CTFE, has a similar effect on the properties of the polymer. 

Figure 2. Chemisorption energies AE of a single fluorine atom adsorbed on the outer surface of the zigzag SWCNTs (p,0) with p = 5 - 15 versus the radius R of the tubes. The solid circles and triangles refer to semiconducting and metallic tubes, respectively.

The correct answer is (A). Fluorine has the smallest atomic radius. The fluorine atom has the highest effective nuclear charge of the elements in the list. Because there are no elements on the list with a greater effective nuclear charge or a smaller amount of shielding, fluorine will have the smallest atomic radius. 

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