(a) Does the lattice energy of an ionic solid increase or decrease
(i) as the charges of the ions increase,
(ii) as the sizes of the ions increase?
(b) Arrange the following substances not listed in Table 8.1 according to their expected lattice energies, listing them from lowest lattice energy to the highest: MgS, KI, GaN, LiBr.
Step 1 of 5) The fact that lighter molecules move at higher average speeds than more massive ones has many interesting applications. For example, developing the atomic bomb during World War II required scientists to separate the relatively low-abundance uranium isotope 235U 10.7%2 from the much more abundant 238U 199.3%2. This separation was accomplished by converting the uranium into a volatile compound, UF6, that was then allowed to pass through a porous barrier (Figure 10.16). Because of the pore diameters, this process is not simple effusion. Nevertheless, the way in which the rate of passing through the pores depends on molar mass is essentially the same as that in effusion. The slight difference in molar mass between 235UF6 and 238UF6 caused the molecules to move at slightly different rates: