Chemical Bonding Ionic Bonding and Ionic Compounds

Objectives: 1.Compare and contrast a chemical formula for a molecular compound with one for an ionic compound. 2.Discuss the arrangement of ions in crystals. 3.Define lattice energy and explain its significance. 4.List and compare the distinctive properties of ionic and molecular compounds 5.Write the Lewis structure for a polyatomic ion.

Ionic Bonding and Ionic Compounds H2OH2O NaCl Ionic Compound – positive and negative ions combined is such a way to yield a neutral compound. Formula unit – simplest ratio of atoms found in an ionic compound

Formation of Ionic Compounds Ionic compounds form as a result of the transfer of elecrons.

Formation of Ionic Compounds

Cations and anions are arranged in a crystal lattice; minimizing potential energy Arrangement among ions represents a balance between attractive and repulsive forces Lattice energy – energy released when an ionic compound forms. CaF 2

Properties of Ionic Compounds Some common properties result form the strong forces of attraction holding the basic units together. High melting and boiling points Hard, but brittle substances Do not conduct electricity in the solid state. Do conduct electricity in molten state. Many dissolve in water and conduct electricity Others…do not dissolve in water.

Polyatomic Ions Group of covalently bonded atoms that have acquired a positive or negative charge and form bonds with other ions. Draw Lewis structures for: NH 4 + NO 3 — SO 4 2- PO 4 3-