1. 8.1 Molecular Compounds > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 8 Covalent Bonding 8.1 Molecular Compounds 8.2 The Nature of Covalent Bonding 8.3 Bonding Theories 8.4 Polar Bonds and Molecules

2. 8.1 Molecular Compounds > 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Although the types of pieces are limited, you can make many different toy models depending on how many pieces you use and how they are arranged. CHEMISTRY & YOU How are atoms joined together to make compounds with different structures?

3. 8.1 Molecular Compounds > 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. CHEMISTRY & YOU Similar to how you can make different types of toy models, there are thousands of different types of molecular structures. How are atoms joined together to make compounds with different structures? Atoms are arranged in different ways in space to form molecules with different molecular structures.

4. 8.1 Molecular Compounds > 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. In nature, only the noble gas elements exist as uncombined atoms. Molecules and Molecular Compounds They are monatomic; that is, they consist of single atoms. Helium, which is less dense than air, is often used to inflate balloons.

5. 8.1 Molecular Compounds > 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. But not all elements are monatomic. Molecules and Molecular Compounds O 2 represents two oxygen atoms that are bonded together. Scuba divers breath compressed air, a mixture that contains oxygen gas.

6. 8.1 Molecular Compounds > 6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds What information does a molecular formula provide? Molecules and Molecular Compounds

7. 8.1 Molecular Compounds > 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A molecular formula shows how many atoms of each element a substance contains. Molecules and Molecular Compounds Representing Molecules

8. 8.1 Molecular Compounds > 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Ionic compounds (metals + non-metals) are generally crystalline solids with high melting points. Other compounds, however, have very different properties.

9. 8.1 Molecular Compounds > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Ionic compounds (metals + non-metals) are generally crystalline solids with high melting points. Other compounds, however, have very different properties. Water (H 2 O) is a liquid at room temperature. Carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) are both gases at room temperature.

10. 8.1 Molecular Compounds > 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. These bonds do not involve the transfer of electrons. Molecules and Molecular Compounds The attractions that hold together the atoms in O 2, H 2 O, CO 2, and N 2 O cannot be explained by ionic bonding.

11. 8.1 Molecular Compounds > 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Ionic bonds form when the combining atoms give up or accept electrons. Another way that atoms can combine is by sharing electrons. Molecules and Molecular Compounds

12. 8.1 Molecular Compounds > 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Sharing Electrons – Atoms that are held together by sharing electrons are joined by a covalent bond.

13. 8.1 Molecular Compounds > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Oxygen gas consists of oxygen molecules; each oxygen molecule consists of two covalently bonded oxygen atoms. Sharing Electrons Molecules and Molecular Compounds A molecule is a neutral group of atoms joined together by covalent bonds. All molecules are compounds but not all compounds are molecules. The word MOLECULE refers only to the bonding of non-metals to non-metals.

14. 8.1 Molecular Compounds > 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Elements that form diatomic molecules include Hydrogen, Oxygen, Nitrogen, Fluorine, Chlorine, Iodine and Bromine. These are known as the DIATOMIC 7 Molecules and Molecular Compounds Sharing Electrons Diatomic molecule — a molecule that contains two identical atoms.

15. 8.1 Molecular Compounds > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A compound composed of molecules is called a molecular compound. –Water is an example of a molecular compound. Molecules and Molecular Compounds Sharing Electrons Molecules can also be made of atoms of different elements.

16. 8.1 Molecular Compounds > 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Representing Molecules The molecular formula of water is H 2 O. Notice that the subscript written after an element’s symbol indicates the number of atoms of each element in the molecule. If there is only one atom, the subscript 1 is omitted but always understood.

17. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Butane is commonly used in lighters and household torches. The molecular formula for butane is C 4 H 10. According to this formula, one molecule of butane contains four carbon atoms and ten hydrogen atoms. Molecules and Molecular Compounds Representing Molecules Butane is also a molecular compound.

18. 8.1 Molecular Compounds > 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The subscripts are not necessarily the lowest whole-number ratios. Molecules and Molecular Compounds Representing Molecules A molecular formula reflects the actual number of atoms in each molecule. Butane is C 4 H 10

19. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. For example, an oxygen molecule consists of two oxygen atoms bonded together; its molecular formula is O 2. Molecules and Molecular Compounds Representing Molecules Note that molecular formulas can also describe molecules consisting of atoms of one element.

20. 8.1 Molecular Compounds > 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. it does not show either the arrangement of the various atoms in space or which atoms are covalently bonded to one another. Molecules and Molecular Compounds Representing Molecules A molecular formula does not tell you about a molecule’s structure.

21. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A variety of diagrams and molecular models can be used to show the arrangement of atoms in a molecule. Molecules and Molecular Compounds Representing Molecules

22. 8.1 Molecular Compounds > 22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. It also shows how the carbon atom in each molecule is in the middle between the two oxygen atoms. The molecular structure of carbon dioxide shows how the three atoms are arranged in a row. Molecules and Molecular Compounds Representing Molecules The arrangement of atoms within a molecule is called its molecular structure.

23. 8.1 Molecular Compounds > 23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The molecular structure of water shows how the oxygen atom is in the middle between the hydrogen atoms. The atoms in water are not arranged in a row. Instead the hydrogen atoms are mainly on one side of the water molecule. Molecules and Molecular Compounds Representing Molecules

24. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The molecular structure of ethanol (C 2 H 6 O) is more complicated. Each carbon is bonded to four atoms, each hydrogen is bonded to one atom, and the one oxygen is bonded to two atoms. Molecules and Molecular Compounds Representing Molecules

25. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Acetylsalicylic acid, also known as aspirin, has a molecular formula of C 9 H 8 O 4. What elements make up acetylsalicylic acid? How many atoms of each element are found in one molecule of acetylsalicylic acid?

26. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Acetylsalicylic acid, also known as aspirin, has a molecular formula of C 9 H 8 O 4. What elements make up acetylsalicylic acid? How many atoms of each element are found in one molecule of acetylsalicylic acid? One molecule of acetylsalicylic acid is made of: Carbon, Hydrogen and Oxygen. 9 carbon atoms, 8 hydrogen atoms, and 4 oxygen atoms.

27. 8.1 Molecular Compounds > 27 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Comparing Molecular and Ionic Compounds What representative units define molecular compounds and ionic compounds? Comparing Molecular and Ionic Compounds

28. 8.1 Molecular Compounds > 28 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The representative unit of a molecular compound is a molecule. For an ionic compound, the representative unit is a formula unit. Comparing Molecular and Ionic Compounds

29. 8.1 Molecular Compounds > 29 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Recall that a formula unit is the lowest whole- number ratio of ions in an ionic compound. It is important not to confuse formula units with molecules. –A molecule is made up of two or more atoms that act as a unit. –No such discrete units exist in an ionic compound, which consists of a continuous array of ions. –There is no such thing as a molecule of beryllium chloride or magnesium sulfide. Comparing Molecular and Ionic Compounds

30. 8.1 Molecular Compounds > 30 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Comparing Molecular and Ionic Compounds Many molecular compounds are gases or liquids at room temperature.

31. 8.1 Molecular Compounds > 31 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Solid molecular compounds tend to have relatively lower melting and boiling points than ionic compounds. Sugar (C 6 H 12 O 6 ) melts sooner than Salt (NaCℓ) Comparing Molecular and Ionic Compounds Many molecular compounds are gases or liquids at room temperature.

32. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Water, which is a molecular compound, and sodium chloride, which is an ionic compound, are compared here. Comparing Molecular and Ionic Compounds Collection of water molecules Molecule of water Chemical formulaH2OH2O Array of sodium ions and chloride ions Formula unit of sodium chloride Chemical formulaNaCl

33. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. How is the formula unit of an ionic compound different from a molecule?

34. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. How is the formula unit of an ionic compound different from a molecule? A molecule is made up of two or more atoms that act as a unit. No such discrete units exist in an ionic compound, which exists as an array of ions.

35. 8.1 Molecular Compounds > 35 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A molecular formula shows how many atoms of each element a substance contains. The representative unit of a molecular compound is a molecule. For an ionic compound, the smallest representative unit is a formula unit. Key Concepts

36. 8.1 Molecular Compounds > 36 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. END OF 8.1