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

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?

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

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; that is, they consist of single atoms. Example: Helium

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 Diatomic molecules HOFNBrICl

8.1 Molecular Compounds > 6 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. A molecule is a neutral group of atoms joined together by covalent bonds.

8.1 Molecular Compounds > 7 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. A molecular formula is the chemical formula of a molecular compound.

8.1 Molecular Compounds > 8 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

8.1 Molecular Compounds > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The molecular structure of carbon dioxide shows how the three atoms are arranged in a row. It also shows how the carbon atom in each molecule is in the middle between the two oxygen atoms. Molecules and Molecular Compounds Representing Molecules The arrangement of atoms within a molecule is called its molecular structure.

8.1 Molecular Compounds > 10 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.

8.1 Molecular Compounds > 11 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?

8.1 Molecular Compounds > 12 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 smallest representative unit is a formula unit. Comparing Molecular and Ionic Compounds

8.1 Molecular Compounds > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Many molecular compounds are gases or liquids at room temperature. In contrast to ionic compounds, which are formed from a metal combined with a nonmetal, 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.

8.1 Molecular Compounds > 14 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

8.1 Molecular Compounds > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. How is the formula unit of an ionic compound different from a molecule?

8.1 Molecular Compounds > 16 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.

8.1 Molecular Compounds > 17 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

8.1 Molecular Compounds > 18 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

8.1 Molecular Compounds > 19 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

8.1 Molecular Compounds > 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. In molecular compounds, bonding occurs when atoms share electrons. In ionic compounds, bonding occurs when electrons are transferred between atoms. BIG IDEA Bonding and Interactions

8.1 Molecular Compounds > 21 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. END OF 8.1