Fluorine, Atomic Number

Under ordinary conditions, elemental fluorine is a greenish-yellow gas consisting of F2 molecules. 

Fluorine compounds have many uses. One of the most notable of these is the manufacture of chlorofluorocarbon compounds known by the trade name Freon. These are chemical combinations of chlorine, fluorine, and carbon, an sample of which is dichlorodifluoromethane, CI2CF2. These compounds used to be widely employed as refrigerant fluids and blowing agents to make foam plastics they were also once widely used as propellants in aerosol spray cans. Uses of chlorofluorocarbons have now been phased out because of their role in destroying stratospheric ozone (discussed with oxygen, above). 

The last element in the period of the periodic table under discussion is neon, Ne. Air is about 2 parts per Aousand neon by volume, and neon is obtained by the distillation of liquid air. Neon is especially noted for its use in illuminated signs that consist of glass tubes containing neon, through which an electrical current is passed, causing the neon gas to emit a characteristic glow. 

In addition to 10 protons, most neon atoms have 10 neutrons in their nuclei, although some have 12, and a very small percentage have 11. As shown by its Lewis symbol, 

In going through the rest of the periodic table, it can be seen that all other atoms with 8 outer electrons, like neon, are also noted for a high degree of chemical stability. In addition to neon, these noble gases are argon (atomic number 18), krypton (atomic 

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Which of these is the ground-state electron configuration for an atom of fluorine (atomic number = 9) ... 

A particular element is defined by its atomic number - the number of protons in the nucleus (which will equal the number of electrons surrounding the nucleus in a neutral atom). For example, iron is the element of atomic number 25, meaning that every iron atom will have 25 protons in its nucleus. Chemists use a one or two-letter symbol for each element to simplify communication iron is given the symbol Fe, from the old Latin word for iron, ferrum. The sum of the protons plus neutrons found in a nucleus is called the mass number. For some elements only one mass number is found in nature. Fluorine (atomic number 9, mass number 19) is an example of such an element. Other elements are found in nature in more than one mass number. Iron is found as mass number 55 (91.52%), 54 (5.90%), 57 (2.245%), and 58 (0.33%). These different mass numbers of the same element are called isotopes, and vary in the number of neutrons found in the nucleus. Atomic weight refers to the average mass found in nature of all the atoms of a particular element the atomic weight of iron is 55.847. For calculation purposes, these... 

List these bonds in order of increasing polarity P-F, S-F, Ga-F, Ge-F (F, fluorine, atomic number g P, phosphorus, atomic number 15 S, sulfur, atomic number 16 Ga, gallium, atomic number 31 Ge, germanium, atomic number 32) ... 

The 19F NMR spectrum (Figure 2(d)) provides information on the number and type of fluorine atoms (number of resonances, areas of resonances, SF) in the molecule and, in the form of couplings, may reveal other magnetic atoms (e.g. H, 31P, 19F) one to four bonds from a fluorine atom. (The maximum distance of four bonds between the coupling nuclei should be considered approximate.) Note that the experimental conditions required for quantitative work, as given in Section 3.5.2, may not necessarily have been obtained, and the areas of the resonances should therefore be considered only approximate. In general, much longer repetition times are needed for quantitative conditions. 

Cesium, atomic number 55, is the most active naturally occurring metal. Francium and radium are radioactive and do not occur in nature in appreciable amounts. Noble gases seldom bond with other elements. They are unreactive, monatomic gases. The most active nonmetal is fluorine, atomic number 9. 

Look up the isotopic composition of fluorine, atomic number 9, on the internet. Add the masses of the subatomic particles composing the flourine atom. Is the sum exactly that of the atomic mass given for F Should it be ... 

Solve The first member of fhe halogen group is fluorine, atomic number 9. 

This question is about the ionic bond formed between the metal lithium (atomic number 3) and the non-metal fluorine (atomic number 9). a How many electrons are there in a lithium atom Draw a diagram to show its electron structure. (You can show the nucleus as a dark circle at the centre.) b How does a metal atom obtain a full outer shell of electrons ... 

Like all analytical techniques, both X-ray powder diffraction and X-ray fluorescence have their advantages and disadvantages. Table I indicates the more important features of the two techniques. In terms of the range of application. X-ray fluorescence analysis allows the quantitation of all elements in the periodic table from fluorine (atomic number 9) upward. Accuracies of a few tenths of a percent are possible, and elements are detectable in most cases to the low parts per million level. X-ray powder diffirac-tometry is applicable to any ordered (crystalline) material, and although it is much less accurate or sensitive than the fluorescence method, it is almost unique in its ability to differentiate phases. 

Fluorine is the most electronegative element and thus can oxidize many other elements to their highest oxidation state. The small size of the fluorine atom facihtates the arrangement of a large number of fluorines around an atom of another element. These properties of high oxidation potential and small size allow the formation of many simple and complex fluorides in which the other elements are at their highest oxidation states. 

The nonbonding electron clouds of the attached fluorine atoms tend to repel the oncoming fluorine molecules as they approach the carbon skeleton. This reduces the number of effective coUisions, making it possible to increase the total number of coUisions and stiU not accelerate the reaction rate as the reaction proceeds toward completion. This protective sheath of fluorine atoms provides the inertness of Teflon and other fluorocarbons. It also explains the fact that greater success in direct fluorination processes has been reported when the hydrocarbon to be fluorinated had already been partiaUy fluorinated by some other process or was prechlorinated, ie, the protective sheath of halogens reduced the number of reactive coUisions and aUowed reactions to occur without excessive cleavage of carbon—carbon bonds or mnaway exothermic processes. 

Health and Safety Factors. The toxicity of aHphatic CFCs and HCFCs generally decreases as the number of fluorine atoms increases (16), as shown in Table 7, but there are exceptions as in the case of 141b vs 142b. Also, some derivatives like HCFC-132b can have low acute but high chronic toxicides (29). 

Ha.logen Compounds. Fluorine is unreactive toward ozone at ordinary temperatures. Chlorine is oxidized to Cl20 and Cl20y, bromine to Br Og, and iodine to I2O2 and I4O2. Oxidation of haUde ions by ozone increases with the atomic number of haUde. Fluoride is unreactive chloride reacts slowly, ultimately forming chlorate and bromide is readily oxidized to hypobromite (38). Oxidation of iodide is extremely rapid, initially yielding hypoiodite the estimated rate constant is 2 x 10 (39). HypohaUte ions are oxidized to haUtes hypobromite reacts faster than hypochlorite (40). 

If 90 is added to the designated R number, the resulting single digits individually reflect, in sequential order, the number of carbon, hydrogen, and fluorine atoms present, respectively. Chlorine is deterrnined by difference, ie, the carbon valency of 4 minus number of H and F atoms. For example, R-12 12 + 90 = 102, indicating 1 carbon, 0 hydrogen, 2 fluorine, and 2 chlorine atoms by difference. 

Up to 20 products with different numbers of fluorine atoms and double bonds have been isolated from the fluonnation of benzene with silver difluoride [d], manganese trifluoride [7], potassium tetrafluoroargentate [d], and potassium hexafluoronickelate [24] The composition of the products depends on the fluorinating agents and on the temperature (Table 1)... 

The reactivities of the substrate and the nucleophilic reagent change vyhen fluorine atoms are introduced into their structures This perturbation becomes more impor tant when the number of atoms of this element increases A striking example is the reactivity of alkyl halides S l and mechanisms operate when few fluorine atoms are incorporated in the aliphatic chain, but perfluoroalkyl halides are usually resistant to these classical processes However, formal substitution at carbon can arise from other mecharasms For example nucleophilic attack at chlorine, bromine, or iodine (halogenophilic reaction, occurring either by a direct electron-pair transfer or by two successive one-electron transfers) gives carbanions These intermediates can then decompose to carbenes or olefins, which react further (see equations 15 and 47) Single-electron transfer (SET) from the nucleophile to the halide can produce intermediate radicals that react by an SrnI process (see equation 57) When these chain mechanisms can occur, they allow reactions that were previously unknown Perfluoroalkylation, which used to be very rare, can now be accomplished by new methods (see for example equations 48-56, 65-70, 79, 107-108, 110, 113-135, 138-141, and 145-146)... 

The halogens are volatile, diatomic elements whose colour increases steadily with increase in atomic number. Fluorine is a pale yellow gas which condenses to a canary yellow liquid, bp — 188.UC (intermediate between N2, bp —195.8°, and O2, bp — 183.0°C). Chlorine is a greenish-yellow gas, bp —34.0°, and bromine a dark-red mobile liquid, bp 59.5° interestingly the colour of both elements diminishes with decrease in temperature and at —195° CI2 is almost colourless and Br2 pale yellow. Iodine is a lustrous, black, crystalline solid, mp 113.6°, which sublimes readily and boils at 185.2°C. 

Fluorine (F, atomic number 9) has seven outer electrons, one unpaired. Because it needs to obtain only one electron to fill its outer shell and gain stability, it is highly reactive. Neon (Ne, atomic number 10), on the other hand, has a filled outer shell. Like helium and its other column mates, the noble gases, neon does not readily react with any element. 

Each fluorine atom needs six electrons to complete its octet the number of electrons required = 4(6) = 24. 

The structure of LiTa02F2, as reported by Vlasse et al. [218], is similar to a ReC>3 type structure and consists of triple layers of octahedrons linked together through their vertexes. The layers are perpendicular to the c axis, and each layer is shifted, relative to the layer below, by half a cell in the direction (110). Lithium atoms are situated in the centers of the tetragonal pyramids (coordination number = 5). The other lithium atoms are statistically distributed along with tantalum atoms (coordination number = 6) at a ratio of 1 3. The sequence of the metal atoms in alternating layers is (Ta-Li) - Ta - (Ta-Li). Positions of oxygen and fluorine atoms were not determined. The main interatomic distances are (in A) Ta-(0, F) - 1.845-2.114 Li-(0, F) - 2.087-2.048 (O, F)-(0,F) - 2.717-2.844. 

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