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Lattice energy - and the particular lattice arrangement The...

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Lattice energy: the energy required to separate completely a mole of a solid ionic compound into its gaseous ions It is a measure of just how much stabilization results from the arranging of oppositely charged ions in an ionic solid. To completely break up a salt crystal: NaCl( s ) -> Na + ( g ) + Cl - ( g ) H lattice = +788 kJ/mol Thus, -788 kJ/mol is given off as heat energy when 1 mol of NaCl is incorporated into the salt lattice. So, forming the ions from Na(g) and Cl(g) requires the input of +147 kJ/mol, these ions incorporate into the salt lattice liberating -788 kJ/mol, for an overall highly exothermic release of -641 kJ/mol. The magnitude of the lattice energy depends upon the charges of the ions, their size
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Unformatted text preview: and the particular lattice arrangement. The potential energy of two interacting charged particles is: Q 1 = charge on first particle Q 2 = charge on second particle d = distance between centers of particles k = 8.99 x 10 9 J m/C 2 Thus, the interaction increases: • As the charges increase • As the two charges are brought closer together The minimum distance between oppositely charged ions is the sum of the atomic (ionic) radii. Although atomic radii do vary, it is not over a considerable range, thus , the attraction between two ions is determined primarily by the charge of the ions ....
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