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The Building Blocks of Matter

- Elements and Atoms. The Building Blocks of Matter. Matter may consist of elements, compounds, or mixtures. - Ionic Bonds. Ions and Ionic Bonds.

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The Building Blocks of Matter

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  1. - Elements and Atoms The Building Blocks of Matter • Matter may consist of elements, compounds, or mixtures.

  2. - Ionic Bonds Ions and Ionic Bonds • You and a friend walk past a market that sells apples for 40 cents each and pears for 50 cents each. You have 45 cents and want an apple. Your friend also has 45 cents but wants a pear.

  3. - Ionic Bonds Ions and Ionic Bonds • When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

  4. - Ionic Bonds Ions and Ionic Bonds • Ions are atoms that have lost or gained electrons.

  5. - Ionic Bonds Ions and Ionic Bonds • Ionic bonds form as a result of the attraction between positive and negative ions.

  6. - Ionic Bonds Properties of Ionic Compounds • In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.

  7. - Ionic Bonds Previewing Visuals • Before you read, preview Figure 17. Then write two questions that you have about the diagram in a graphic organizer like the one below. As you read, answer your questions. Formation of an Ionic Bond Q. What is an ionic bond? A. An ionic bond is the attraction between two oppositely charged ions. Q. What is the overall charge on an ionic compound? A. Overall, an ionic compound is electrically neutral.

  8. - Ionic Bonds Salt • Click the Video button to watch a movie about salt.

  9. - Ionic Bonds Links on Ionic Compounds • Click the SciLinks button for links on ionic compounds.

  10. End of Section:Ionic Bonds

  11. - Covalent Bonds How Covalent Bonds Form • The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.

  12. - Covalent Bonds How Covalent Bonds Form • The oxygen atom in water and the nitrogen atom in ammonia are each surrounded by eight electrons as a result of sharing electrons with hydrogen atoms.

  13. - Covalent Bonds How Covalent Bonds Form • An oxygen molecule contains one double bond, while a carbon dioxide molecule has two double bonds. A nitrogen molecule contains one triple bond.

  14. - Covalent Bonds Comparing Molecular and Ionic Compounds • The table compares the melting points and boiling points of a few molecular compounds and ionic compounds. Use the table to answer the following questions.

  15. Check that the graphs are correctly set up and labeled before students plot the data. Graphing: Create a bar graph of just the melting points of these compounds. Arrange the bars in order of increasing melting point. The y-axis should start at –200ºC and go to 900ºC. - Covalent Bonds Comparing Molecular and Ionic Compounds

  16. Melting points of molecular compounds are lower than those of ionic compounds. Interpreting Data: Describe what your graph reveals about the melting points of molecular compounds compared to those of ionic compounds. - Covalent Bonds Comparing Molecular and Ionic Compounds

  17. Molecular compounds have weak attractive force between molecules, so less energy is needed to melt molecular compounds. Inferring: How can you account for the differences in melting points between molecular compounds and ionic compounds? - Covalent Bonds Comparing Molecular and Ionic Compounds

  18. Boiling points of molecular compounds are lower than those of ionic compounds. Interpreting Data: How do the boiling points of the molecular and ionic compounds compare? - Covalent Bonds Comparing Molecular and Ionic Compounds

  19. Students may predict that ammonia is a molecular compound because it has relatively low melting and boiling points. Predicting: Ammonia’s melting point is –78ºC and its boiling point is –34ºC. Is ammonia a molecular compound or an ionic compound? Explain. - Covalent Bonds Comparing Molecular and Ionic Compounds

  20. - Covalent Bonds Unequal Sharing of Electrons • Fluorine forms a nonpolar bond with another fluorine atom. In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.

  21. - Covalent Bonds Unequal Sharing of Electrons • A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. In contrast, a water molecule is a polar molecule because of its bent shape.

  22. Question Answer - Covalent Bonds Asking Questions • Before you read, preview the red headings. In a graphic organizer like the one below, ask a what or how question for each heading. As you read, write answers to your questions. How do covalent bonds form? Covalent bonds form when two atoms share electrons. What are molecular compounds? Molecular compounds are compounds that contain molecules bonded with covalent bonds. How does unequal sharing of electrons affect the atoms in molecular compounds? Unequal sharing of electrons causes the bonded atoms to have slight electrical charges.

  23. - Covalent Bonds Links on Molecular Compounds • Click the SciLinks button for links on molecular compounds.

  24. End of Section:Covalent Bonds

  25. - Bonding in Metals Metallic Bonding • A metal crystal consists of positively charged metal ions embedded in a “sea” of valence electrons.

  26. - Bonding in Metals Metallic Properties • The “sea of electrons” model of solid metals explains their ability to conduct heat and electricity, the ease with which they can be made to change shape, and their luster.

  27. - Bonding in Metals Relating Cause and Effect • As you read, identify the properties of metals that result from metallic bonding. Write the information in a graphic organizer like the one below. Effects Electrical conductivity Heat conductivity Cause Metallic bonding Ductility Malleability Luster

  28. - Bonding in Metals Links on Metallic Bonding • Click the SciLinks button for links on metallic bonding.

  29. End of Section:Bonding in Metals

  30. Graphic Organizer Polar Covalent Bond Nonpolar Covalent Bond Metallic Bond Feature Ionic Bond Attraction between positive ions and surrounding electrons. Attraction between oppositely charged ions How Bond Forms Equal sharing of electrons Unequal sharing of electrons Charge on Bonded Atoms? Yes, slightly positive or slightly negative Yes; positive or negative No Yes; positive H2O molecule (or other polar covalent molecule) NaCl crystal (or other ionic compound) Example Calcium (or other metal) O2 molecule

  31. End of Section:Graphic Organizer

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