Conductivity, electrical proton

Covalent bonding, in all the cases so far quoted, produces molecules not ions, and enables us to explain the inability of the compounds formed to conduct electricity. Covalently bonded groups of atoms can, however, also be ions. When ammonia and hydrogen chloride are brought together in the gaseous state proton transfer occurs as follows ... 

That is, the H-bonded network provides a natural route for rapid transport. This phenomenon of proton jumping thus occurs with little actual movement of the water molecules themselves. Ice has an electrical conductivity close to that of water because such proton jumps also readily occur even when the water molecules are fixed in a crystal lattice. Such conduction of protons via H-bonded networks has been offered as an explanation for a number of rapid proton transfers of biological significance. 

Despite this enormous viscosity, fused H3PO4 (and D3PO4) conduct electricity extremely well and this has been shown to arise from extensive self-ionization (autoprotolysis) coupled with a proton-switch conduction mechanism for the... 

The Contact between Solvent and Solute Particles Molecules and Molecular Ions in Solution. Incomplete Dissociation into Free Ions. Proton Transfers in Solution. Stokes s Law. The Variation of Electrical Conductivity with Temperature. Correlation between Mobility and Its Temperature Coefficient. Electrical Conductivity in Non-aqueous Solvents. Electrical Conduction by Proton Jumps. Mobility of Ions in D20. 

Electrical Conduction by Proton Jumps. As mentioned in Sec. 24, a hydroxyl ion may be regarded as a doubly charged oxygen ion 0 , containing a proton inside the electronic cloud of the ion, which has the same number of electrons as a fluoride ion. The radius of the hydroxyl ion cannot be very different from that of the fluoride ion. But it will be seen from Table 2 that the mobility of the hydroxyl ion is about four times as great. This arises from the fact that a large part of the mobility is undoubtedly due to proton transfers.1 Consider a water molecule in contact with a hydroxyl ion. If a proton jumps from the molecule to the ion,... 

Besides these special physical properties, hydrogen-bonded liquid water also has unique solvent and solution properties. One feature is high proton (H ) mobility due to the ability of individual hydrogen nuclei to jump from one water molecule to the next. Recalling that at temperatures of about 300 K, the molar concentration in pure water of H3O ions is ca. 10 M, the "extra" proton can come from either of two water molecules. This freedom of to transfer from one to an adjacent "parent" molecule allows relatively high electrical conductivity. A proton added at one point in an aqueous solution causes a domino effect, because the initiating proton has only a short distance to travel to cause one to pop out somewhere else. 

Radioactive substances also have life-saving uses. A radioactive form of cobalt is extensively used in radiation therapy for cancer patients. The treatment was first developed by Harold Johns (1915—) in Canada, where he pioneered cobalt therapy units at the University of Saskatchewan. One of the artificially made elements, Americium (atomic number 95, i.e., with 95 protons in its atomic nucleus), is another life-saving radioactive element. As it decays, it emits alpha particles, which strip electrons from surrounding gas molecules ionized air conducts electricity much better than air containing smoke particles, and the reduction in conductivity produced by smoke is what triggers the alarm in smoke detectors. 

Give the number of protons, neutrons, and elec- 10. Which elements best conduct electricity ... 

Condensed states of matter liquids and solids. (16.1) Conduction bands the molecular orbitals that can be occupied by mobile electrons, which are free to travel throughout a metal crystal to conduct electricity or heat. (16.4) Conjugate acid the species formed when a proton is added to a base. (7.1)... 

Recent studies on DNA-M adducts have also revealed possible semiconductor properties of these structures. In this context, of particular mention are the experiments of Lee et al. (1993), who demonstrated M-DNA formation by coordinative binding of the Zn ion to the N3 imino proton of thymine in the nucelobase pair A-T, and to the Ni proton of guanine in the C-G nucleo-base pair (Figure 7.9). The so-called engineered DNA - which is referred to as M-DNA - is able to conduct electricity. 

Along with the increase in the number of electrons comes an increase in the number of protons in the atoms nuclei. The increase in the magnitude of positive electrical charge in the nucleus increases the electrostatic force of attraction the nucleus exerts on all of an atom s electrons, with the result that atoms tend to decrease in size as one moves across a row of the periodic table from left to right. Thus, the atoms of nonmetallic elements tend to be much smaller than the atoms of metallic elements, with helium atoms being the smallest atoms of all elements. One consequence of the smaller size is that nonmetals have little tendency to give up electrons, so that nonmetals do not conduct electricity. 

Bipolar electrolysis systems are characterized by the type of electrolyte. The proton exchange membrane (PEM) system, developed by the General Electric Compare (GE), uses as the electrolyte a thin membrane of sulfonated fiuorocaibon (Nation ) that conducts electricity when saturated with water. Electrodes are formed by depositing a thin platinum film on opposite sides of the merrtbrane to form a bipolar cell. An electrolyzer is made by stacking 50-200 cells in series, with srritably formed separators to direct the exhaust gases into charmels at the sides. Since the membrane is the electrolyte, only pine water needs to be supphed to the cell. When the cell oper-... 

To better understand what the ampere represents, we need to take a closer look at the behavior of material at the subatomic level. In Chapter 9 we esplained what is meant by atoms and molecules. An atom has three major subatomic pardcles, namely, electrons, protons, and neutrons. Neutrons and protons form the nucleus of an atom. How a material conducts electricity is influenced by the number and the arrangement of electrons. Electrons have negarive charge, whereas protons have a positive charge, and neutrons have no charge. 

The a.c.-impedance method described in the previous chapter is often employed to characterize the electrical properties of solid proton conductors. The method gives a rapid answer to the question does the material under investigation conduct electricity and the method is not critical with respect to size, shape and quality of the sample used. 

The heart of a fuel cell is a polymer, proton-conductive membrane. On both sides of the membrane there is a porous electrode. The electrodes must be porous because the reactant gases are fed from the back and must reach the interface between the electrodes and membrane, where the electrochemical reactions take place in the so called catalyst layer, or more precisely, on the catalyst surface. Technically, the catalyst layer may be a part of the porous electrode or part of the membrane, depending on the manufacturing process. The multilayer assembly of the membrane sandwiched between the two electrodes is commonly called the membrane electrode assembly or MEA. The MEA is then sandwiched between the collector/separator plates—"collector" because they collect and conduct electrical current and "separator" because in multicell configuration they separate the gases in the adjacent cells. At the same time, in multicell configuration they physically/electrically connect the cathode... 

A new mechanism by which poly(aniline) conducts electricity has been established by J. P. Travers and M. Nechtschein. The conduction process can be accounted for in terms of electrons hopping between localized states under the assistance of proton transfer, for which the presence of water plays an essential role [107] (Figure 12). 

Teissie and coworkers detected rapid lateral movement of protons on a phospholipid monolayer-water interface by a number of measurements fluorescence from a pH indicator dye near the membrane surface, electrical surface conductance, and surface potentiaL These investigators found that the conduction of protons along the surface is considerably faster than proton conduction in the bulk phase (2 to 3 min versus 40 min for a comparable distance in their measurement setup). This novel conduction mechanism is proton-specific, as confirmed by a radioactive electrode measurement as well as by replacement with deuterated water. It is a consequence of cooperativity between neighboring phospholipid molecules the conduction mechanism disappears when phospholipid molecules are not in contact with each other. 

Because water is not protonated in these solutions, its addition reduces the concentration of ions, and therefore the electrical conductivity. The conductivity reaches a minimum in solutions containing 97% of acid, but rises on further dilution as a result of the formation of nitrate and hydroxonium ions. ... 

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