Metal electron loss

Thus, the reaction by which a metal dissolves in an acid is conveniently discussed in terms of oxidation and reduction involving electron transfer. The reaction can be divided into half-reactions to show the electron gain (by H+ ions) and the electron loss (by metal atoms). 

The periodic table can help us decide what type of ion an element forms and what charge to expect the ion to have. Fuller details will be given in Chapter 2, but we can begin to see the patterns. One major pattern is that metallic elements— those toward the left of the periodic table—typically form cations by electron loss. Nonmetallic elements—those toward the right of the table—typically form anions by gaining electrons. Thus, the alkali metals form cations, and the halogens form anions. 

To predict the electron configuration of a monatomic cation, remove outermost electrons in the order np, ns, and (n — l)d fora monatomic anion, add electrons until the next noble-gas configuration has been reached. The transfer of electrons results in the formation of an octet (or duplet) of electrons in the valence shell on each of the atoms metals achieve an octet (or duplet) by electron loss and nonmetals achieve it by electron gain. 

The effect of ionizing radiation on molecular or ionic solids is to eject electrons, which often subsequently react at sites in the material well removed from the residual electron-loss centre. These electron-loss and electron-gain centres, or breakdown products thereof, are paramagnetic and have been extensively studied by e.s.r. spectroscopy. Results for a wide range of organo metals both as pure compounds and as dilute solid solutions are used to illustrate this action. Aspects of the electronic structures of these centres are derived from the spectra and aspects of redox mechanisms are discussed. 

Figure 2.8. Electron density contours for atomic chemisorption on jellium with electron density that corresponds to A1 metal. Upper row Contours of constant electron density in the plane normal to the surface. Center row Difference in charge density between isolated adatom and metal surface, full line gain and dashed line loss of charge density. Bottom row Bare metal electron density profile. Reproduced from [30].

Figure 2.25. Charge density difference plot of N2 adsorbed on Ni(100). Regions of electron loss are indicated with dashed outer line and increase with full line. We have chosen a plane containing the interacting metal atom with one N2 molecule in the same plane. From Ref. [3].

From this it may be seen that the reactions that occur at the two terminals of a battery employing metals as both terminals are dependent on the relative tendencies of the two metals toward loss of electrons. Consequently, any further study of battery cells should be based on some suitable quantitative expression of these tendencies. 

The key points from these experiments are that the more easily replaceable monophosphine ligands are required for the reduction of N2, which is favored by the presence of oxo-anions. Thus, as the reaction proceeds and electron density passes from metal to N2, the 7r-acceptor phosphines are replaced successively by 7r-donor oxo species. This change in ligand encourages further release of metal electron density onto the bound, partially reduced N2, which results in its protonation. This resulting effective increase in the oxidation state of the metal then causes further substitution of the softer phosphines by the harder oxo-anions. These mutually enhancing effects result ultimately in complete loss of all phosphine ligands and the production of NH3. 

Zinc metal (Zn) loses electrons to form the positive ion, Zn2+. The zinc is oxidized by the process of electron loss. The hydrogen ions, H+, gain electrons to become neutral hydrogen gas (H2), so the hydrogen ions are reduced. The chlorine ions do not change and are called spectator ions , so the equation could be simplified to show only the things that change ... 

The ligand-bridged complexes [Rh2(CO)4 (PPh3) (/x-RNXNR)2] (n = 1 or 2, R = aryl, X = N or CMe) undergo reversible one-electron oxidation to isolable monocations (275), which appear to be fully delocalized mixed valence complexes (276). Oxidation also leads to enhanced susceptibility to carbonyl substitution ( = 1, X = CMe), and a drastic shortening in the metal-metal bond distance implies electron loss from an anti-bonding dimetal orbital (275) (Section III,F). 

Overpotential loss is inversely proportional to the electrochemically active area. Thus, a composite anode with three phases is preferred, i.e., ceramic (ionic conduction), metallic (electronic conduction) and pore (gas diffusion) phases mixed together to expand the electrochemically active area to a three-dimensional anode volume. ... 

The forward steps of H2 oxidative addition, equations (a) and (e), are usually considered to be promoted by coordinatively unsaturated metal centers in initially low oxidation states (i.e., high metal basicity). Loss of electrons via the oxidation is compensated for by a gain of electrons through an increase in the coordination number . This also explains why the earlier transition metal systems (d -d ) tend to form complexes of higher coordination number than those of the later d -d systems (especially Group... 

The process of surface electrooxidation is an electrochemical situation in which the electrons are lost in the outer layer of the metal/solution interface. During the process, the metal atom undertakes the formation of either a metallic cation or a surface oxide. The electron loss goes with an increase in the electron density by the oxidizing agent. The formation of a soluble species on non-noble metals containing oxygenated molecules or the formation of noble metal oxides is probably one of the most studied topics in this field. 

Across a period, the elements become less metallic and more nonmetallic with corresponding changes in chemical properties. The arrangement of the elements in the periodic table makes it easier to see trends in their properties within groups and across periods. Two important properties of elements are the size of their atoms and the ease (or lack of ease) with which they lose an electron. Both are functions of the periodic similarities of electronic configuration, causing both size and ease of electron loss to be periodic properties of the elements. 

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