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Ionic Bondin1 - sodium cations and chloride anions and...

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Ionic Bonding Ionic Solids When cations and anions precipitate out of a saturated solution they crystallize into a  lattice arrangement that maximizes the attractive forces between cations and anions  while minimizing the repulsive forces between ions of the same charge. For example,  shown below is the arrangement of ions found in crystalline sodium chloride. The chloride ions are represented as green, and the sodium ions as yellow in this figure.  To better understand the energetics of this arrangement let's examine Coulomb's Law for  the potential energy of interaction between two charges: In NaCl we have three types of Coulombic interactions, an attractive interaction between 
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Unformatted text preview: sodium cations and chloride anions, and repulsive interactions between sodium cations and between chloride anions. For a mole of solid NaCl, the sum of all these Coulombic energies for all cations and anions in a crystal is -861 kJ/mole. Na + (g) + Cl-(g) NaCl → (s) U = -861 kJ/mole Δ Lattice Energy- change in energy when completely gaseous atoms are brought together into 1 mole of a solid ionic substance. As we see from Coulomb's law, the lattice energy is related to the charge and distance between ions in the solid. Smaller the ions will have smaller distances between them in a solid, and thus have higher lattice energies....
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