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Table of Contents

Table of Contents. Elements and Atoms Atoms, Bonding, and the Periodic Table Ionic Bonds Covalent Bonds Bonding in Metals. - Elements and Atoms. The Building Blocks of Matter. Matter may consist of elements, compounds, or mixtures. - Elements and Atoms. Atomic Theory and Models.

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Table of Contents

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  1. Table of Contents • Elements and Atoms • Atoms, Bonding, and the Periodic Table • Ionic Bonds • Covalent Bonds • Bonding in Metals

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

  3. - Elements and Atoms Atomic Theory and Models • Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.

  4. - Elements and Atoms Atomic Theory and Models • Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.

  5. - Elements and Atoms Atomic Theory and Models • Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.

  6. - Elements and Atoms Atomic Theory and Models • Through the first part of the twentieth century, atomic models continued to change.

  7. - Elements and Atoms Outlining Elements and Atoms • As you read, make an outline about elements and atoms. Use the red headings for the main ideas and the blue headings for the supporting ideas. • The Building Blocks of Matter • Elements, Compounds, and Mixtures • Particles of Elements • Atomic Theory and Models • Dalton’s Atomic Theory • Thomson and Smaller Parts of Atoms • Rutherford and the Nucleus • Bohr’s Model • A Cloud of Electrons • The Modern Atomic Model

  8. - Elements and Atoms More on Atomic Structure • Click the PHSchool.com button for an activityabout atomic structure.

  9. End of Section:Elements and Atoms

  10. - Atoms, Bonding, and the Periodic Table Valence Electrons and Bonding • The number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.

  11. - Atoms, Bonding, and the Periodic Table The Periodic Table • Elements are organized into rows and columns based on their atomic number.

  12. - Atoms, Bonding, and the Periodic Table Periodic Table Activity • Click the Active Art button to open a browser window and access Active Art about the periodic table.

  13. - Atoms, Bonding, and the Periodic Table The Periodic Table • As the number of protons (atomic number) increases, the number of electrons also increases. As a result, the properties of the elements change in a regular way across a period.

  14. - Atoms, Bonding, and the Periodic Table The Periodic Table • The variety of colors in a “neon” sign results from passing an electric current through sealed glass tubes containing different noble gases.

  15. Key Terms: Key Terms: Examples: Examples: halogen atomic number alkali metal period group family noble gas - Atoms, Bonding, and the Periodic Table Building Vocabulary • After you read the section, reread the paragraphs that contain definitions of Key Terms. Use the information you have learned to write a definition of each Key Term in your own words. Key Terms: Examples: valence electrons Valence electrons are electrons that are of the highest energy level and are held most loosely. A halogen is any element in Group 17, which consists of elements with seven valence electrons. The atomic number of an element is the number of protons in the nucleus of an atom. electron dot diagram The symbol for the element surrounded by dots that stand for valence electrons is an electron dot diagram. A alkali metal is any element in Group 1, which consists of elements with one valence electron. A row of elements across the periodic table is called a period. chemical bond A chemical bond is the force of attraction that holds two atoms together as a result of the rearrangement of electrons between them. Elements in the same column are called a group or family. A noble gas is any element in Group 18, which consists of elements with eight valence electrons. symbol Each element is represented by a symbol, usually consisting of one or two letters.

  16. End of Section:Atoms, Bonding, and the Periodic Table

  17. - 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.

  18. - 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.

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

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

  21. For example, during the reaction of sodium with chlorine: sodium (on the left) loses its one valence electron to chlorine (on the right), resulting in a positively charged sodium ion (left) and a negatively charged chlorine ion (right). The reaction of sodium with chlorine

  22. - 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.

  23. - 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.

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

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

  26. End of Section:Ionic Bonds

  27. - 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.

  28. - 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.

  29. - 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.

  30. - 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.

  31. 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

  32. 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

  33. 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

  34. 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

  35. 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

  36. - 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.

  37. - 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.

  38. 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.

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

  40. End of Section:Covalent Bonds

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

  42. - 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.

  43. - 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

  44. - Bonding in Metals Links on Metallic Bonding • Click the SciLinks button for links on metallic bonding. Formation of a metallic bond in Mg

  45. End of Section:Bonding in Metals

  46. 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

  47. End of Section:Graphic Organizer

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