5. Formation of Ionic Compound s Compounds composed of cations and anions are called ionic compounds. Although they are composed of ions, ionic compounds are electrically neutral. The electrostatic forces that hold ions together in ionic compounds are called ionic bonds. Section 7.2 – Ionic Bonds & Ionic Compounds

Formation of Ionic Compounds (cont.) Formula Units A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. A formula unit is the lowest whole-number ratio of ions in an ionic compound. NaCl is the chemical formula for sodium chloride.

6. Properties of Ionic Compounds Most ionic compounds are crystalline solids at room temperature. Ionic compounds generally have high melting points. The orderly arrangement of component ions produces the beauty of crystalline solids.

Properties of Ionic Compounds (cont.) The coordination number of an ion is the number of ions of opposite charge that surround the ion in a crystal. In NaCl, each ion has a coordination number of 6. In CsCl, each ion has a coordination number of 8. In TiO 2, each Ti 4+ ion has a coordination number of 6, while each O 2- ion has a coordination number of 3.

Properties of Ionic Compounds (cont.) Ionic compounds can conduct an electric current when melted or dissolved in water. When this occurs the compound is called an electrolyte

END OF SECTION 7.2