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8.1 Molecular Compounds > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 8 Covalent Bonding 8.1 Molecular Compounds.

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Presentation on theme: "8.1 Molecular Compounds > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 8 Covalent Bonding 8.1 Molecular Compounds."— Presentation transcript:

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. Molecules and Molecular Compounds What information does a molecular formula provide? Molecules and Molecular Compounds

4 8.1 Molecular Compounds > 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. In nature, only the noble gas elements, such as helium and neon, exist as uncombined atoms. Molecules and Molecular Compounds They are monatomic; so they consist of single atoms. But not all elements are monatomic. Oxygen exists in molecules as O 2.

5 8.1 Molecular Compounds > 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Ionic compounds are generally crystalline solids with high melting points. Other compounds, however, have very different properties.

6 8.1 Molecular Compounds > 6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Ionic compounds 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.

7 8.1 Molecular Compounds > 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. These bonds do not involve the transfer of electrons. Another way that atoms can combine is by sharing 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.

8 8.1 Molecular Compounds > 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Remember that ionic bonds form when the combining atoms give up or accept electrons. Molecules and Molecular Compounds Sharing Electrons –Atoms that are held together by sharing electrons are joined by a covalent bond.

9 8.1 Molecular Compounds > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sharing Electrons Molecules and Molecular Compounds A molecule is a neutral group of atoms joined together by covalent bonds. An oxygen molecule is an example of a diatomic moleculea molecule that contains two atoms, like oxygen, O 2.

10 8.1 Molecular Compounds > 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A compound composed of molecules is called a molecular compound. H 2 O is an example of a molecular compound. A molecular formula is the chemical formula of a molecular compound. Molecules and Molecular Compounds Sharing Electrons Molecules can also be made of atoms of different elements.

11 8.1 Molecular Compounds > 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. A molecular formula shows how many atoms of each element a substance contains. The molecular formula of carbon dioxide is CO 2. The subscript written after an elements symbol shows the number of atoms of each element in the molecule. Molecules and Molecular Compounds

12 8.1 Molecular Compounds > 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Butane is 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 C atoms and ten H atoms. Molecules and Molecular Compounds Representing Molecules Butane is another a molecular compound.

13 8.1 Molecular Compounds > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Molecules and Molecular Compounds Representing Molecules A molecular formula does not tell you how the atoms are arranged in space or which atoms are bonded to one another structure. The arrangement of atoms within a molecule is called its molecular structure.

14 8.1 Molecular Compounds > 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The molecular structure of CO 2 shows how the 3 atoms are arranged in a row. It also shows how the C atom is in the middle between the two oxygen atoms. Molecules and Molecular Compounds Representing Molecules

15 8.1 Molecular Compounds > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The molecular structure of ethanol (C 2 H 6 O) is more complicated. Each C is bonded to four atoms, each H is bonded to one atom, and the one oxygen is bonded to two atoms. Molecules and Molecular Compounds Representing Molecules

16 8.1 Molecular Compounds > 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Comparing Molecular and Ionic Compounds What representative units define molecular compounds and ionic compounds? The representative unit of a molecular compound is a molecule. For an ionic compound, the smallest representative unit is a formula unit. Comparing Molecular and Ionic Compounds

17 8.1 Molecular Compounds > 17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Many molecular compounds are gases or liquids at room temperature. Comparing Molecular and Ionic Compounds Molecular compounds tend to have relatively lower melting and boiling points than ionic compounds.

18 8.1 Molecular Compounds > 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Many molecular compounds are gases or liquids at room temperature. Most molecular compounds are composed of atoms of two or more nonmetals. Comparing Molecular and Ionic Compounds Molecular compounds tend to have relatively lower melting and boiling points than ionic compounds.

19 8.1 Molecular Compounds > 19 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

20 8.1 Molecular Compounds > 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. How is the formula unit of an ionic compound different from a molecule?

21 8.1 Molecular Compounds > 21 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.

22 8.1 Molecular Compounds > 22 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

23 8.1 Molecular Compounds > 23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. covalent bond: a bond formed by the sharing of electrons between atoms molecule: a neutral group of atoms joined by covalent bonds diatomic molecule: a molecule consisting of two atoms Glossary Terms

24 8.1 Molecular Compounds > 24 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. molecular compound: a compound that is composed of molecules molecular formula: a chemical formula of a molecular compound that shows the kinds and numbers of atoms present in a molecule of a compound Glossary Terms

25 8.1 Molecular Compounds > 25 Questions 1.What is a covalent bond? 2.List three examples of covalent bonding. 3. What is a molecule? 4. What is a molecular formula? 5. What is the representative unit in a molecular compound? 6. List two ways that molecular compounds are different from ionic compounds. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.


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