Enthalpies ionization

There is an excellent correlation between these data and the gas-phase data, in terms both of the stability order and the energy differences between carbocations. A plot of the gas-phase hydride affinity versus the ionization enthalpy gives a line of slope 1.63 with a correlation coefficient of 0.973. This result is in agreement with the expectation that the gas-phase stability would be somewhat more sensitive to structure than the solution-phase stability. The energy gap between tertiary and secondary ions is about 17kcal/mol in the gas phase and about 9.5 kcal/mole in the SO2CIF solution. 

Here 1 is the third ionization enthalpy of the lanthanide element and I(MCln,s) is AH for the following reaction ... 

Fig. 1.1 (a) The ionization enthalpies of dipositive lanthanide ions with configurations of the type [Xe]4f" (upper plot left-hand axis), (b) The standard Gibbs energy change of reaction 1 (lower plot right-hand axis estimated value ... 

The lattice enthalpy, Aiatt//m, is the molar enthalpy change accompanying the formation of a gas of ions from the solid. Since the reaction involves lattice disruption the lattice enthalpy is always large and positive. Aatom//m and Adiss//m are the enthalpies of atomization (or sublimation) of the solid, M(s), and the enthalpy of dissociation (or atomization) of the gaseous element, X2(g). The enthalpy of ionization is termed electron gain enthalpy, Aeg//m, for the anion and ionization enthalpy, Ajon//m, for the cation. 

Figure 7.9 Thermodynamic data (b)-(d) needed in analysis of the enthalpy of formation of the binary transition metal compounds given in (a), (b) Atomization enthalpy of first series transition metals (c) sum of first and second ionization enthalpies of first series transition metals (d) derived lattice enthalpy of transition metal dihalides.

Adiabatic detachment energy [7]. Abbreviations used rcoy (Em) = covalent radius of element E in a trivalent compound BE(E-E) = bond enthalpy of a single E-E bond D°298(E2) = dissociation enthalpy of the E2 molecule at standard conditions IE = ionization enthalpy EA = electron affinity AHf°(E2 g) = standard enthalpy of formation of the gaseous E2 molecule. 

Europium and ytterbium di-valence. The oxidation state II for Eu and Yb has already been considered when discussing the properties of a number of divalent metals (Ca, Sr, Ba in 5.4). This topic was put forward again here in order to give a more complete presentation of the lanthanide properties. The sum of the first three ionization enthalpies is relatively small the lanthanide metals are highly electropositive elements. They generally and easily form in solid oxides, complexes, etc., Ln+3 ions. Different ions may be formed by a few lanthanides such as Ce+4, Sm+2, Eu+2, Yb+2. According to Cotton and Wilkinson (1988) the existence of different oxidation states should be interpreted by considering the ionization... 

Experimental and theoretical studies of the basicity and acidity of benzene-substituted indoles were performed169. In aqueous solution, the pK values are above —4 for the bases and above 15 for the acids. Gas-phase ionization enthalpies have been calculated using the AMI semiempirical method. 

It follows that the calorimetry of HA might provide both the ionization enthalpy of HA, (AH)y [see Eq. (19)] and the ionization constant Kha ... 

Calorimetric results are also subject to medium effects and—when necessary—appropriate corrections must be applied in order to obtain truly thermodynamic ionization enthalpies (and, eventually, ionization constants). 

Calorimetric data on azoles are given in Tables II and III. Figure 1 shows the linear relationship between the ionization enthalpies (AH°) and free energies (AG°). It is noteworthy that protonation and deprotonation generate two nearly parallel lines. Di- and tri-positive (or negative) ions are clearly off these lines, suggesting that the AH° — AG° relationship is sensitive to the overall charge of the ions. 

The crystal of CaO assumes the NaCl structure, the closest approach between positive and negative ions being 239 pm. The enthalpy of atomization of calcium metal is 193 kJ mol that of dioxygen is 248 kJ moT1 (of oxygen atoms). The two electron attachment enthalpies of oxygen are -148 and +838 kJ mol respectively. The first and second successive ionization enthalpies of calcium are 596 and 1156 kJ mol respectively. Use the data to calculate a value for the standard enthalpy of formation of calcium oxide and compare the result with the experimental value of -635 kJ mol... 

The overall change of enthalpy represents the enthalpy of formation of the hydrated cation, Mz + (aq), and has a value as given in Tables 2.2 and 2.3 for particular cases. The value consists of contributions from the enthalpy of atomization of element M and the appropriate sum of its ionization enthalpies, and the enthalpy of hydration of the gaseous ion. 

The common oxidation states are -3, +3 and +5, but the simple ions As3-, As3+ and As5+ are not known. The krypton electronic structure could be attained by gain of three electrons, but there is a high energy requirement. Equally, the loss of five valence electrons to form As5+ is unrealizable because of the high ionization enthalpy. 

Covalent radius (A) Ionic radius (A)(xx) Ionization enthalpy (cV) Crystal Structure... 

Because the slope for the ter /-butyl halides in Table 4 seems rather larger than the others when perhaps they should be more equal, we would like to estimate the enthalpy of formation of tert-bvXy fluoride in yet another way. We should be able to use the ionization enthalpies (and associated assumptions of Reference 42) of z-PrF, i-PrCl, t-BuF and -BuC1 with SbF5 in S02C1F by simply assuming ... 

After substituting the requisite ionization enthalpies of both the ter /-butyl and isopropyl halides, we conclude that the reaction in equation 8... 

The terms AHam and AHax constitute the enthalpies of atomization of the element and the nonmetal respectively, AHei is the ionization enthalpy of the metal, AHae is the ionization enthalpy of the nonmetal, and U0 is the lattice energy. For gaseous diatomic nonmetals, AHax is the enthalpy for dissociation (i.e., bond energy... 

The standard enthalpy of electron gain of a molecular entity X is opposite to the standard ionization enthalpy of its negative ion, Aion TP(X ). 

Metal Radii (pm), Atom Radii (pm), Ion M-M Bond Energy (kj mol-1) Ionization Enthalpy (k mol-1) -A Hhyd (k mol-1) Charge to Size Ratio... 

As a result of the low ionization enthalpies for the outer electrons and the sphericity and low polarizability of the resulting M+ ions, the chemistry of these elements is principally that of their +1 ions. No other cations are known or, in view of the values of the second ionization enthalpies, expected. The ions M, where the s shell is filled, are discussed in Section 3-4. 

Electronic Configuration Metal Radius (A) Ionization Enthalpies (kJ mol1) AHd,J (kJ mol-1)... 

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