Presentation on theme: "Ionic Bonding. Metal atoms with low ionization energies and non-metal atoms with high electron affinity form cations (+) and anions (-) Oppositely charged."— Presentation transcript:
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 Ionic Bonding
Coulomb’s Law The energy of interaction between the pair of ions can be calculated Where Q 1 and Q 2 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
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
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?
Which substance would have a higher melting point : NaF or CsI? Which would have a higher lattice energy: FeO or Fe 2 O 3 ?
Ionic Structures Can have many types of arrangements Arrangement depends on the charge and size of the ions involved
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.
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 Mg 2+, Ca 2+, Ca
Isoelectric Series Comparitive sizes of ions all possessing the same number of electrons As nuclear charge increases, the radius decreases O 2- > F - > Na + > Mg 2+ > Al 3+
Example Arrange the ions S 2-, K +, Ca 2+, and Cl - in order of decreasing size.