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Ionic Bonding

Ionic Bonding. Ionic Bonding. Metal atoms with low ionization energies and non-metal atoms with high electron affinity form cations (+) and anions (-) Oppositely charged ions attract to a crystalline structure. Coulomb’s Law.

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Ionic Bonding

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  1. Ionic Bonding

  2. Ionic Bonding • Metal atoms with low ionization energies and non-metal atoms with high electron affinity form cations (+) and anions (-) • Oppositely charged ions attract to a crystalline structure

  3. Coulomb’s Law • The energy of interaction between the pair of ions can be calculated • Where Q1and Q2 are the charges of the ions and r the distance between the ion’s centers • Since one charge is always + and the other -, the energy will be a negative number • The ion pair has lower energy than separate ions

  4. Lattice Energy • Quantity of energy required for 1 mole of the solid ionic substance to be separated into its ions • Higher the negative value (exothermic) the more stable the compound • The higher the lattice energy of an ionic compound the harder, more brittle, and the higher the melting, boiling and vaporization points

  5. Crystal Lattice Strength • Based on Coulomb’s Law, we expect that ionic solids formed by smaller atoms or by atoms that have greater charge, will be stronger • Example: Why is the lattice energy for MgO about four times greater than the lattice energy form NaF?

  6. Which substance would have a higher melting point : NaF or CsI? • Which would have a higher lattice energy: FeO or Fe2O3?

  7. Ionic Structures • Can have many types of arrangements • Arrangement depends on the charge and size of the ions involved

  8. Forming The Ions • The ions are formed when electrons are transferred from the atom with low electronegativity to an atom with high electronegativity • Predict the compound formed between aluminum and fluorine.

  9. Sizes of Ions • Cations are smaller than their parents • Anions are larger than their parents • Ions of the same charge, size increases going down a group • List the following in order of decreasing size Mg2+, Ca2+, Ca

  10. Isoelectric Series • Comparitive sizes of ions all possessing the same number of electrons • As nuclear charge increases, the radius decreases • O2- > F- > Na+ > Mg2+ > Al3+

  11. Example • Arrange the ions S2- , K+ , Ca2+, and Cl- in order of decreasing size.

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