Chemical Bonds •Three basic types of bonds: -Ionic •Electrostatic attraction between ions -Covalent •Sharing of electrons -Metallic •Metal atoms bonded to several other atoms… Energetics of Ionic Bonding As we saw in the last chapter, it takes 495 kJ/mol to remove electrons from sodium. Energetics of Ionic Bonding Energetics of Ionic Bonding We get 349 kJ/mol back by giving electrons to chlorine. Energetics of Ionic Bonding Energetics of Ionic Bonding But these numbers don’t explain why the reaction of sodium metal and chlorine gas to form sodium chloride is so exothermic!….

Lattice Energy •This third piece of the puzzle is the lattice energy: The energy required to completely separate a mole of a solid ionic compound into its gaseous ions. •The energy associated with electrostatic interactions is governed by Coulomb’s law: E el = ? Q 1 Q 2 d…

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