P08 - NaCl 5.14 ev / atom- 3.75 ev / atom 1.39 ev / atom...

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Packing of Spheres in a Solid - Potential Energy is a function of geometry and bonding forces of attraction/repulsion - To maximize coordination between ions - greater energy gain in crystal than in isolated molecule due to periodicity - coordination of maximum number of near neighbors is determined by size of ions Solve Triangle r + + r - ( ) 2 = r - 2 + r - 2 r + + r - ( ) 2 = 2 r - 2 r + + r - = 2 r - r - r - + r + = 1 2 r - = 2 - 1 ( ) r - r + r - =1.414- 1®\ r + r - = 0.414 If the radii have 0.414 as a ration, then it has a coordination number of 6, but all ions must be in contact with each other . 12.) Lowering of energy by electron exchange Na ® Na + + e - ¥ ( ) Cl + e - (¥ ) ® Cl - Na + Cl +1.39 ev
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Unformatted text preview: NaCl 5.14 ev / atom- 3.75 ev / atom 1.39 ev / atom must supply this energy to ionize, but once done, the minimization of E more than compensates for this En minimize E by maximizing number of near neighbors of opposite charge 1.) Neutral atom (alkalai metal) takes expenditure of energy; Ionization energy 2.) Neutral atom (halogen) has takes a gain in energy; electron affinity 3.)There is still a net expenditure of energy- Paulie Exclusion Principle- Repeating order of ionization energies due to position in periodic table...
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