Transition metal ionization energy

Raghavachari, K., Trucks, G.W., Highly Correlated Systems, Ionization Energies of First Row Transition Metals Sc-Zn, Journal of Chemical Physics, 1989 91 2457-2460. 

C08-0023. Iron and cobalt form compounds that can be viewed as containing cations, but nickel does not. Use the ionization energies in Appendix C to predict which other transition metal elements are unlikely to form stable cations with charges greater than +2. 

The chemistry of the transition metals is determined in part by their atomic ionization energies. Metals of the 3d and 4d series show a gradual increase in ionization energy with atomic number (Z), whereas the trend for the 5d series is more pronounced (Figure 20-3). First ionization energies for transition metals in the 3d and 4d series are between 650 and 750 kJ/mol, somewhat higher than the values for Group 2 alkaline earth metals but lower than the typical values for nonmetals in the p block. 

The first ionization energies of transition metals show gradual upward trends across each row of the periodic table. 

C20-0037. In each of the following pairs of transition metals, select the one with the higher value for the indicated property and give the reason (a) melting points of Pd and Cd (b) densities of Cu and Au and (c) first ionization energies of Cr and Co. 

In the isoelectronic zirconates this absorption band is not observed [17]. The spectral position of these MMCT bands has been interpreted in terms of the relevant ionization potentials [17], an approach which runs parallel with the Hush theory [10]. The fact that the MMCT transition is at higher energy in the Cr(III)-Ti(IV) pair than in the Fe(II)-Ti(IV) pair is due to the more than 10 eV higher ionization potentials of the trivalent transition-metal ions compared to the divalent transition-metal ions. The fact that the MMCT absorption band is not observed in the zirconates in contradiction to the titanates is due to the higher ionization potential of the Ti(III) species ... 

Fig. 6. The ionization potentials of the second transition metal row as a function of metal atom. The energies of a single 157 nm and 193 nm photon are indicated as dashed lines. L and H denote an atom with a low-spin or a high-spin ground electronic state,...

Presently, the gas phase photofragmentation of several transition metal cluster complexes is reviewed. The techniques employed for these gas phase studies rely on sensitive ionization detection and the use of a broad range of excitation energies. 

The model of metal-ammonia solutions that has emerged is based on ionization of the metal atoms to produce metal ions and electrons that are both solvated. The solvated electron is believed to reside in a cavity in ammonia, and thus it may behave as a particle in a three-dimensional box with quantized energy levels. Transitions between the energy levels may give rise to absorption of light and thereby cause the solutions to be colored. The dissolution process can be represented as... 

A measure of the Lewis acidity of a metal ion is determined by its affinity for a pair of electrons, and the greater this affinity, the more stable the complexes formed by the metal ion will be. However, removing electrons from a metal to produce an ion is also related to the attraction the metal atom has for electrons. Therefore, it seems reasonable to seek a correlation between the stability constants for complexes of several metals with a given ligand and the total energy necessary for ionization to produce the metal ions. The first-row transition metal ions react in solution with ethylenediamine, en, to form stable complexes. We will consider only the first two steps in complex formation, which can be shown as follows ... 

Cyclic chain termination with aromatic amines also occurs in the oxidation of tertiary aliphatic amines (see Table 16.1). To explain this fact, a mechanism of the conversion of the aminyl radical into AmH involving the (3-C—H bonds was suggested [30]. However, its realization is hampered because this reaction due to high triplet repulsion should have high activation energy and low rate constant. Since tertiary amines have low ionization potentials and readily participate in electron transfer reactions, the cyclic mechanism in systems of this type is realized apparently as a sequence of such reactions, similar to that occurring in the systems containing transition metal complexes (see below). 

Transition metals tend to have higher melting points than representative metals. Because they are metals, transition elements have relatively low ionization energies. Ions of transition metals often are colored in aqueous solution. Because they are metals and thus readily form cations, they have negative standard reduction potentials. Their compounds often have unpaired electrons because of the diversity of -electron configurations, and thus, they often are paramagnetic. Consequently, the correct answers are (c) and (e). 

Bare metal cations can be prepared from almost any inorganic source as long as enough energy is given to the sample to allow dissociation, vaporization, and ionization. Metal anions are less well studied due to the low electron affinities of most transition metals. Where M+ and M ions are compared, the M ions are generally less reactive. 

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