Thermochemical properties of gaseous Li2 and Li3

Abstract

Using the Knudsen effusion mass spectrometric technique, the gas species Li(g), Li2(g), and Li3(g) have been observed over liquid lithium. The atomization energies of Li2(g) and Li3(g):D 0° (Li2) =25.5±1.5 kcal/mole and D 0° (Li3) =41.5±4.0 kcal/mole, were derived from the study of the various gaseous equilibria: Li(s,l) →Li(g) (1), 2Li(s,l) →Li2(g) (2), Li2(g) →2Li(g) (3), 3Li(s,l) →Li3(g) (4), 2Li2(g) →Li3(g)+Li(g) (5). The following heats of formation were also obtained: ΔH 0° (Li) =38.5±1.0 kcal/mole, ΔH 0° (Li2) =51.5±2.0 kcal/mole, ΔH 0° (Li3) =73.0±4.0 kcal/mole. The ionization potentials of Li2 and Li3 were determined as 4.86±0.1 and 4.35±0.2 eV, respectively, from which the binding energies D 0° (Li+ 2) =37.7±2.0 and D 0° (Li+ 3) =65.5±4.3 kcal/mole result.