Chapter 7 Ionic and Metallic Bonding 7.2 Ionic Bonds and 7.1 Ions 7.2 Ionic Bonds and Ionic Compounds 7.3 Bonding in Metals Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Where does table salt come from? 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. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Formation of Ionic Compounds What is the electrical charge of an ionic compound? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Formation of Ionic Compounds Although they are made of ions, ionic compounds are electrically neutral. The total positive charge of the cations equals the total negative charge of the anions. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Formation of Ionic Compounds Ionic Bonds The electrostatic forces that hold ions together in ionic compounds are called ionic bonds. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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-to-one ratio, and both ions have stable octets. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Formation of Ionic Compounds Ionic Bonds Aluminum metal (Al) and the nonmetal bromine (Br2) react violently to form the ionic solid aluminum bromide (AlBr3). Each bromine atom has seven valence electrons and readily gains one additional electron. Three bromine atoms combine with each aluminum atom. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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. NaCl is the chemical formula for sodium chloride. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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 whole-number ratio of ions in an ionic compound. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Formation of Ionic Compounds Formula Units For sodium chloride, the lowest whole-number ratio of the ions is 1:1 (one Na+ ion to each Cl– ion). The formula unit for sodium chloride is NaCl. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Predicting Formulas of 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 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Solve Apply the concepts to this problem. Sample Problem 7.1 Solve Apply the concepts to this problem. 2 a. Start with the atoms. • • • K and O • • • • Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Solve Apply the concepts to this problem. Sample Problem 7.1 Solve Apply the concepts to this problem. 2 a. In order to have a completely filled valence shell, the oxygen atom must gain two electrons. These electrons come from two potassium atoms, each of which loses one electron. K • • • O + K+ 2– Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Solve Apply the concepts to this problem. Sample Problem 7.1 Solve Apply the concepts to this problem. 2 a. Express the electron dot structure as a formula. The formula of the compound formed is K2O (potassium oxide). Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Solve Apply the concepts to this problem. Sample Problem 7.1 Solve Apply the concepts to this problem. 2 b. Start with the atoms. Mg and N • • • Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Solve Apply the concepts to this problem. Sample Problem 7.1 Solve Apply the concepts to this problem. 2 b. Each nitrogen atom needs three electrons to have an octet, but each magnesium atom can lose only two electrons. Three magnesium atoms are needed for every two nitrogen atoms. • • • N 3– + Mg2+ Mg Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Solve Apply the concepts to this problem. Sample Problem 7.1 Solve Apply the concepts to this problem. 2 b. Express the electron dot structure as a formula. The formula of the compound formed is Mg3N2 (magnesium nitride). Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine. • • F • + Ca2+ – Ca CaF2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Properties of Ionic Compounds What are three properties of ionic compounds? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Properties of Ionic Compounds Most ionic compounds are crystalline solids at room temperature. The component ions in such crystals are arranged in repeating three-dimensional patterns. The beauty of crystalline solids comes from the orderly arrangement of their component ions. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Properties of Ionic Compounds Ionic compounds generally have high melting points. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Properties of Ionic Compounds Ionic compounds can conduct an electric current when melted or dissolved in water. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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

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

Properties of Ionic Compounds Ionic compounds also conduct electric current if they are dissolved in water. When dissolved, the ions are free to move about in the solution. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Questions What is the electrical charge on an ionic compound? What is an ionic bond? What does a chemical formula show? Write the chemical formula for the compound that is formed when: a. calcium reacts with oxygen b. sodium reacts with nitrogen c. potassium reacts with sulfur 5. What are three properties of ionic compounds? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

ionic compound: a compound composed of positive and negative ions Glossary Terms ionic compound: a compound composed of positive and negative ions ionic bond: the electrostatic attraction that binds oppositely charged ions together chemical formula: an expression that indicates the number and type of atoms present in the smallest representative unit of a substance Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Glossary Terms formula unit: the lowest whole-number ratio of ions in an ionic compound; in magnesium chloride, the ratio of magnesium ions to chloride ions is 1:2 and the formula unit is MgCl2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.