Ionic Bonds and Ionic Compounds

7.2Page 194

Formation of Ionic Compounds

• Compounds composed of cations or anions are called ionic compounds.

• Usually composed of metal cations and nonmetal anions.– NaCl

• Ionic compounds are electrically neutral.– The total positive charge of cations equals the

total negative charge of anions.

Ionic Bonds

• Anions and cations attract one another by their electrostatic forces. These forces are called Ionic Bonds.

• When sodium and chlorine react to form a compound, the sodium atom gives its one valence electron to a chlorine atom.

• They form an ionic bond in a one-to-one ratio.

Formation of Ionic Compounds

Forming Ionic Compounds

• Show how Bromine (Br) reacts with Aluminum (Al).

Formula Units

• Chemist represent the composition of substances by writing chemical formulas.

• Chemical formulas show the kinds and numbers of atoms in the smallest representative unit of a substance. They actually refer to ratio known as a formula unit.– The lowest whole-number ratio of ions in an ionic

compound.– Write the formula unit for Magnesium chloride.

Properties of Ionic Compounds

• Most are crystalline solids at room temperature.

• Arranged in repeating three-dimensional patterns.

• Have high melting points.• Can conduct an electric current when melted

or dissolved in water.

Coordination Number

• The number of ions of opposite charge that surround the ion in a crystal.

• See page 198.