Charge number, definition

The coordinate pertaining to solvent reorganization, z, is the same fictitious charge number as already considered in the Hush-Marcus model of outer-sphere electron transfer (Section 1.4.2), and so is the definition of 2q [equation (1.27)] and the difference between the Hush and Marcus estimation of this parameter. The coordinated describing the cleavage of the bond is the bond length, y, referred to its equilibrium value in the reactant, yRX. Db is the bond dissociation energy and the shape factor ft is defined as... 

AG, 2 is calculated from electrochemical data using the definition of the standard potential (Equation 1.67), where n is the charge number of the reaction, that is, the number of electrons involved, and F is the Faraday constant. In convenient units, F = 23.06 kcal/(molV). 

Although the entire hydronium ion carries a positive charge, we can ask, Which atom, in a formal sense, bears the charge To determine formal charge, we consider each atom to own all of its unshared electrons plus only half of its shared electrons (one electron from each covalent bond). We then subtract this total from the number of valence electrons in the neutral atom to get the formal charge. This definition can be expressed in equation form as follows ... 

Fig. 5.38 Defect concentrations of our model oxide as a function of the partial pressure of oxygen (Kroger-Vink or Brouwer diagram). The Brouwer approximation is naturally no longer applicable at the crossing points, and the transitions are smoothed. The partial pressure of the intrinsic point (index i) is indicated. Note that the charge number z is included in the definition of the ordinate.

Na and Nb are the numbers of atoms in the two groups A and B and S is the switching function. With the group-based switching function, it is necessary to define the distance between the two groups (i.e. the two points Ta and Tb). There is no definitive way to do this. As with cutoffs, a special marker atom can be nominated within each residue, or the centre of mass, centre of geometry or centre of charge may be used. 

Short chains of amino acid residues are known as di-, tri-, tetrapeptide, and so on, but as the number of residues increases the general names oligopeptide and polypeptide are used. When the number of chains grow to hundreds, the name protein is used. There is no definite point at which the name polypeptide is dropped for protein. Twenty common amino acids appear regularly in peptides and proteins of all species. Each has a distinctive side chain (R in Figure 45.3) varying in size, charge, and chemical reactivity. 

Plasma can be broadly defined as a state of matter in which a significant number of the atoms and/or molecules are electrically charged or ionized. The generally accepted definition is limited to situations whereia the numbers of negative and positive charges are equal, and thus the overall charge of the plasma is neutral. This limitation on charge leaves a fairly extensive subject area. The vast majority of matter ia the universe exists ia the plasma state. Interstellar space, interplanetary space, and even the stars themselves are plasmas. 

At any interface between two different phases there will be a redistribution of charge in each phase at the interface with a consequent loss of its electroneutrality, although the interface as a whole remains electrically neutral. (Bockris considers an interface to be sharp and definite to within an atomic layer, whereas an interphase is less sharply defined and may extend from at least two molecular diameters to tens of thousands of nanometres the interphase may be regarded as the region between the two phases in which the properties have not yet reached those of the bulk of either phase .) In the simplest case the interface between a metal and a solution could be visualised as a line of excess electrons at the surface of the metal and an equal number of positive charges in the solution that are in contact with the metal (Fig. 20.2). Thus although each phase has an excess charge the interface as a whole is electrically neutral. 

Every atom contains a definite number of electrons. This number, which runs from 1 to more than 100, is characteristic of a neutral atom of a particular element All atoms of hydrogen contain one electron all atoms of the element uranium contain 92 electrons. We will have more to say in Chapter 6 about how these electrons are arranged relative to one another. Right now, you need only know that they are found in the outer regions of the atom, where they form what amounts to a cloud of negative charge. 

Since m2 < mi (by definition), H2 must be greater than ni and it is not unreasonable to assume that n2 = ni - -1, i.e. the number of charges on the ions differs by one (this assumption is borne out by the validity of the expression when subsequently applied to all electrospray spectra). We may therefore write the following equation, containing a single unknown i, which may be solved readily ... 

By definition the partial current density ij is the number of charges that in unit time cross the unit cross-sectional area due to the migration of ions j that is,... 

The concept of the oxidation state of an element in a chemical compound has a long and confusing history. In the most pretentious form of the concept the oxidation state or oxidation number is the electrical charge localised on the concerned atom in the compound. Confusion arises when we realise that the definition of the atomic domain is arbitrary and the experimental determination of the electrical charge in the once chosen domain is often problematic. 

On trying to assign an oxidation number to the copper atom one finds that the atomic charges, as calculated with the MuUiken definition 183), are remarkably small ... 

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