Estimation of thermodynamic and physicochemical properties of the alkali astatides: On the bond strength of molecular astatine (At2) and the hydration enthalpy of astatide (At −)

AbstractThe recent accurate and precise determination of the electron affinity (EA) of the astatine atom At0 warrants a re-investigation of the estimated thermodynamic properties of At0 and astatine containing molecules as thisEA was found to be much lower (by 0.4  eV) than previous estimated values. In this contribution we estimate, from available data sources, the following thermodynamic and physicochemical properties of the alkali astatides (MAt, M = Li, Na, K, Rb, Cs): their solid and gaseous heats of formation, lattice and gas-phase binding enthalp ies, sublimation energies and melting temperatures. Gas-phase charge-transfer dissociation energies for the alkali astatides (the energy requirement for M+At−➔ M0 + At0) have been obtained and are compared with those for the other alkali halides. Use of Born-Haber cycles together with the newAE (At0) value allows the re-evaluation of ΔHf (At0)g (=56  ± 5 kJ/mol); it is concluded that (At2)g is a weakly bonded species (bond strength<50  kJ/mol), significantly weaker bonded than previously estimated (116 kJ/mol) and much weaker bonded than I2 (148  kJ/mol), but in agreement with the finding from theory that spin-orbit coupling considerably reduces the bond strength in At2. The hydration enthalpy ( ΔHaq) of At− is estimated to be −230 ± 2 kJ/mol (using ΔHaq[H+] =  −1150.1 kJ/mol), in good agreement with molecular dynamics calculations. Arguments are presented that the largest alka...

Source: Journal of Mass Spectrometry - March 16, 2024 Category: Chemistry Authors: Peter C. Burgers, Lona Zeneyedpour, Theo M. Luider, John L. Holmes Tags: RESEARCH ARTICLE Source Type: research