7 2 Ionic Bonds and Ionic Compounds Chapter

7. 2 Ionic Bonds and Ionic Compounds > Chapter 7 Ionic and Metallic Bonding 7. 1 Ions 7. 2 Ionic Bonds and Ionic Compounds 7. 3 Bonding in Metals 1 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > CHEMISTRY & YOU Where does table salt come from? In some countries, salt is obtained by the evaporation of seawater. In other countries, salt is mined from rock deposits deep underground. 2 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Sodium chloride, or table salt, is an ionic compound consisting of sodium cations and chloride anions. • An ionic compound is a compound composed of cations and anions. 3 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Although they are composed of ions, ionic compounds are electrically neutral. • The total positive charge of the cations equals the total negative charge of the anions. 4 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Ionic Bonds Anions and cations have opposite charges and attract one another by means of electrostatic forces. • The electrostatic forces that hold ions together in ionic compounds are called ionic bonds. 5 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Ionic Bonds When sodium and chlorine react to form a compound, the sodium atom transfers its one valence electron to the chlorine atom. • Sodium and chlorine atoms combine in a one-toone ratio, and both ions have stable octets. 6 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Formula Units A chemical formula shows the numbers of atoms of each element in the smallest representative unit of a substance. • Na. Cl is the chemical formula for sodium chloride. 7 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Formula Units Ionic compounds do not exist as discrete units, but as collections of positively and negatively charged ions arranged in repeating patterns. 8 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Formula Units The chemical formula of an ionic compound refers to a ratio known as a formula unit. • A formula unit is the lowest wholenumber ratio of ions in an ionic compound. 9 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Formation of Ionic Compounds Formula Units For sodium chloride, the lowest wholenumber ratio of the ions is 1: 1 (one Na+ ion to each Cl– ion). • The formula unit for sodium chloride is Na. Cl. • Although ionic charges are used to derive the correct formula, they are not shown when you write the formula unit of the compound. 10 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Sample Problem 7. 1 Predicting Formulas of Ionic Compounds Use electron dot structures to predict the formulas of the ionic compounds formed from the following elements: a. potassium and oxygen b. magnesium and nitrogen 11 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > 12 Copyright © Pearson Education, Inc.

7. 2 Ionic Bonds and Ionic Compounds > Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine. 13 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds What are

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds 1) Most ionic compounds are crystalline solids at room temperature. The beauty of crystalline solids comes from the orderly arrangement of their component ions. 15 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds Each ion is attracted strongly to each of its neighbors, and repulsions are minimized. • The large attractive forces result in a very stable structure. 16 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds 2) Ionic compounds generally have high melting points. 17 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds 3) Ionic compounds can conduct an electric current when melted or dissolved in water. 18 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds When sodium chloride is melted, the orderly crystal structure breaks down. Power source • If a voltage is applied across this molten mass, cations migrate freely to one electrode and anions migrate to the other. Current meter Flow of electrons Inert metal electrodes Flow of electrons Cl– Na+ To (+) electrode To (–) electrode • This movement of electrons allows electric current to flow between the electrodes through an external wire. 19 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds This solar facility uses molten Na. Cl for its ability to absorb and hold a large quantity of heat, which is used to generate electricity. 20 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds The coordination number of an ion is the number of ions of opposite charge that surround the ion in a crystal. • In Na. Cl, each ion has a coordination number of 6. – The coordination number of Na+ is 6 because each Na+ ion is surrounded by six Cl– ions. – The coordination number of Cl– is also 6 because each Cl– ion is surrounded by six Na+ ions. 21 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds In Cs. Cl, each ion has a coordination number of 8. • Each Cs+ ion is surrounded by eight Cl– ions. • Each Cl– ion is surrounded by eight Cs+ ions. 22 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > Properties of Ionic Compounds Titanium dioxide (Ti. O 2), or rutile, forms tetragonal crystals. • The coordination number for the cation (Ti 4+) is 6. – Each Ti 4+ ion is surrounded by six O 2– ions. • The coordination number of the anion (O 2–) is 3. – Each O 2– ion is surrounded by three Ti 4+ ions. 23 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > When can ionic compounds conduct an electric current? A. Only when melted B. When melted or dissolved in water C. Only when dissolved in water D. When solid or melted 24 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.

7. 2 Ionic Bonds and Ionic Compounds > When can ionic compounds conduct an electric current? A. Only when melted B. When melted or dissolved in water C. Only when dissolved in water D. When solid or melted 25 Copyright © Pearson Education, Inc. , or its affiliates. All Rights Reserved.