1. Chapter 4 Compounds and Their Bonds 4.8 Attractive Forces in Compounds 1 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh EditionCopyright © 2012 by Pearson Education, Inc.

2. Dipole-Dipole Attractions and Hydrogen Bonds In covalent compounds, polar molecules exert attractive forces called dipole-dipole attractions form strong dipole attractions called hydrogen bonds between hydrogen atoms bonded to very electronegative atoms of F, O, or N Hydrogen bonds are the strongest force between molecules and play a major role in the shape of DNA. 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

3. Dispersion Forces Dispersion forces are weak attractions between nonpolar molecules caused by temporary dipoles that develop when molecules bump into each other weak, but make it possible for nonpolar molecules to form liquids and solids 3 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

4. Comparison of Bonding and Attractive Forces 4 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

5. Melting Points and Attractive Forces Melting points of compounds are related to the strength of attractive forces between molecules or compounds are lower due to weak forces such as dispersion forces are higher due to stronger attractive forces such as hydrogen bonding are highest in ionic compounds due to the strong attractive forces between ions in the compound 5 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

6. Melting Points of Selected Substances 6 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

7. Learning Check Identify the main type of attractive forces that are present in liquids of the following compounds: ionic bonds, dipole- dipole, hydrogen bonds, or dispersion forces. A. NCl 3 B. H 2 O C. Br-Br D. KCl E. NH 3 7 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

8. Solution Identify the main type of attractive forces that are present in liquids of the following compounds: ionic bonds, dipole- dipole, hydrogen bonds, or dispersion forces. A. NCl 3 dipole-dipole forces B. H 2 Ohydrogen bonds C. Br-Brdispersion forces D. KClionic bonds E. NH 3 hydrogen bonds 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.