2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Compounds and Molecules What Are Compounds? Chemical bonds distinguish compounds from mixtures. A compound is held together by chemical bonds. A chemical bond is the attractive force that holds atoms or ions together. A compound always has the same chemical formula. Chapter 5

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Compounds Section 1 Compounds and Molecules Chapter 5

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Bond Section 1 Compounds and Molecules Chapter 5

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Compounds and Molecules What Are Compounds? continued Chemical structure shows the bonding within a compound. A chemical structure is the arrangement of atoms in a substance. A bond length is the average distance between the nuclei of two bonded atoms. A bond angle is the angle formed by two bonds to the same atom. Chapter 5

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bond Length Section 1 Compounds and Molecules Chapter 5

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Bond Angle Section 1 Compounds and Molecules Chapter 5

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Compounds and Molecules How Does Structure Affect Properties? Compounds with network structures are strong solids. Example: Quartz is made of silicon and oxygen atoms bonded in a strong, rigid structure: Chapter 5

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Compounds and Molecules How Does Structure Affect Properties? continued Compounds made of networks of bonded ions have high melting points and boiling points. Example: Table salt—sodium chloride—is made of a tightly packed repeating network of positive sodium ions and negative chlorine ions. Chapter 5

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Compounds and Molecules How Does Structure Affect Properties? continued Some compounds are made of molecules. Some compounds made of molecules are solids, others are liquids, others are gases. The strength of attractions between molecules varies. Attractions between water molecules are called hydrogen bonds. Hydrogen bonding is depicted on the next slide. Chapter 5

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Water Bonding Section 1 Compounds and Molecules Chapter 5

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Ionic and Covalent Bonding What Holds Bonded Atoms Together? continued Bonds can bend and stretch without breaking. Although a “bar” is sometimes used to represent a bond between two atoms, chemical bonds behave more like flexible springs. Chapter 5

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Ionic and Covalent Bonding Metallic Bonds A metallic bond is a bond formed by the attraction between positively charged metal ions and the electrons around them. Electrons move freely between metal atoms. This model explains why metals: conduct electricity conduct heat are flexible Chapter 5