Sodium transfer

The oppositely charged Na+ and Cl- ions that result when sodium transfers an electron to chlorine are attracted to one another by electrostatic forces, and we say that they are joined by an ionic bond. The crystalline substance that results is said to be an ionic solid. A visible crystal of sodium chloride does not consist of individual pairs of Na+ and Cl- ions, however. Instead, solid NaCl consists of a vast three-dimensional network of ions in which each Na+ is surrounded by and attracted to many Cl - ions, and each Cl- is surrounded by and attracted to many Na+ ions (Figure 6.7). 

In Section 3.1 you learned that the electronegativity difference for the bond between sodium and chlorine is 2.1. Thus, the bond is an ionic bond. Sodium has a very low electronegativity, and chlorine has a very high electronegativity. Therefore, when sodium and chlorine interact, sodium transfers its valence electron to chlorine. As shown in Figure 3.9, sodium becomes Na+ and chlorine becomes Cl . 

Potassium leaves the cell, while the net flow of sodium is inward. A nonequilibrium stationary state for the cell at rest is maintained by the sodium and potassium pumps, which pump out the entering sodium ions and pump the leaking potassium ions back into the cell interior, using a certain metabolic output. The sodium transfer is coupled with the chemical reaction. The electrochemical potential difference for sodium ions is expressed as... 

Sodium transfers a single electron to the aromatic system to produce a pentadienyl radical anion, 5-48. This anion is protonated at the position either ortho or meta to the rr-donating methoxy group to give an interme-... 

Sodium Transfer to Silicate and Sulphate Phases. The flame... 

Now he must weigh the sodium. A 100 ml beaker is filled halffull of the petroleum distillate from the can of sodium, or with xylene. He puts it on the scale and weighs it. He needs 34.5 grams of sodium metal, so with a clean sharp knife, he cuts off a chunk of sodium, transfers it to the beaker and weighs it. If it is not quite 34.5 grams, he cuts a little more sodium and adds it to the beaker. This is done quickly, so that evaporation of the petroleum does not throw the measurement off. Then another 100 ml beaker is filled half-full of anhydrous ethyl ether. The sodium metal is transferred to it with a spoon. The petroleum is poured back in with the block of sodium and the can sealed up so that it does not evaporate. With a clean sharp knife, the sodium is cut up into little pieces about 1/2 the size of a pea. 

The water transfer coefficient of a membrane depends directly on anolyte and catholyte concentrations. The amount of water transferred across the membrane per mole of sodium transferred, called the water transfer coefficient, decreases with increasing... 

Figure 3. Schematic of sodium transfer system for EBR-II model...

Qualitatively, this picture is relatively simple to understand in terms of the mobilities of the anions involved. Quantitatively, the picture is rather complex, particularly when the ion sizes are not too different. In the case of p-toluenesulfonate (with a small solution cation), anion transfer is the thermodynamically preferred process, but the greater mobility of a small cation makes the latter transfer kineticaUy more facile. Consequently, the dominant process is timescale dependent. Furthermore, as indicated in Sect. 2.7.3.7.1, the presence of salt within the film is electrolyte concentration dependent. Cations (coions) can only be ejected from the fihn if they are present in the first place, that is, if the film is nonpermselective. The complexities of this process have only recently been unraveled [149, 150) and the EQCM response (film composition) is dependent upon the experimental timescale (e.g. voltammetric scan rate), film history (first or subsequent redox cycle after equi-hbration), and electrolyte concentration. Fihn mass changes during redox cycling are nonmonotonic on short timescales cation (sodium) transfer is the predominant mode of satisfying electroneutrahty... 

Fig. 23 Combined EQCM/PBD responses of a polypyrrole film to redox switching in sodium salicylate solution. Electrode Au (area = 0.23 cm ) on 10-MHz AT-cut quartz crystal. Solution aqueous 0.5 mol dm sodium salicylate. Potential step program as shown in panel (a). Dotted line in panel (d) represents prediction, based on current trace of panel (b), of salicylate but no sodium transfer to satisfy electroneutrality. (Reproduced from Ref. [147] with permission from The Electrochemical Society.)...

From the Gamma spectrometry investigations, fuei-to-sodium transfer coefficients were determined for noble gases, aerosols, light metals and metalloids. These coefficients are of course provisional until the complete PEE will allow determination of the actual amount of defect foel to be considered. 

Both elements are toxic because they can alter a biological molecule by forcefully exchanging electrons with it. Sodium transfers electrons to the molecule, and chlorine transfers electrons away from the molecule. 

Up to this point, we ve treated chemical bonds as either ionic or covalent. The bond in sodium chloride, for instance, is ionic. Sodium transfers an electron to chlorine to give Na" " and Cl ions, which are held together in the solid by electrostatic attractions between the unlike charges. The C-C bond in ethane, however, is covalent. The two bonding electrons are shared equally by the two equivalent carbon atoms, resulting in a symmetrical electron... 

In 1982, Samec et al. studied the kinetics of assisted alkali and alkali-earth metal cation-transfer reactions by neutral carrier and conclnded that the kinetics of transfer of the monovalent ions were too fast to be measured [186]. In 1986, Kakutani et al. published a study of the kinetics of sodium transfer facilitated by di-benzo-18-crown-6 using ac-polarography [187]. They concluded that the transfer mechanism was a TIC process and that the rate constant was also high. Since then, kinetic studies of assisted-ion-transfer reactions have been mainly carried out at micro-lTlES. In 1995, Beattie et al. showed by impedance measurements that facilitated ion-transfer (FIT) reactions are somehow faster than the nonassisted ones [188,189]. In 1997, Shao and Mirkin used nanopipette voltammetry to measure the rate constant of the transfer of K+ assisted by the presence of di-benzo-18-crown-6, and standard rate constant values of the order of 1 cm-S were obtained [190]. A more systematic study was then published that showed the following sequence,, which is not in accordance with... 

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