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Chapter 7 Ionic Bonding

Chapter 7 Ionic Bonding. Modified from Dr. Cotton’s Presentation. Section 7.1 - Ions. OBJECTIVES: Determine the number of valence electrons in an atom of a representative element. Section 7.1 - Ions. OBJECTIVES: Explain octet rule. Section 7.1 - Ions. OBJECTIVES:

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Chapter 7 Ionic Bonding

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  1. Chapter 7Ionic Bonding Modified from Dr. Cotton’s Presentation

  2. Section 7.1 - Ions • OBJECTIVES: • Determine the number of valence electrons in an atom of a representative element.

  3. Section 7.1 - Ions • OBJECTIVES: • Explain octet rule

  4. Section 7.1 - Ions • OBJECTIVES: • Describe how cations form.

  5. Section 7.1 - Ions • OBJECTIVES: • Explain how anions form.

  6. Valence Electrons are… • responsible for chemical properties • Valence electrons - The s and p electrons in the outer energy level • Core electrons -those in the energy levels below.

  7. Keeping Track of Electrons • Atoms in the same column... • same outer electron configuration. • same valence electrons. • Number of valence electrons = the group number for a representative element • Group 2A: Be, Mg, Ca, etc. • have 2 valence electrons

  8. Electron Dot diagrams are… • A way keeping track of valence electrons. • Write the symbol - it represents the nucleus and inner (core) electrons • Put one dot for each valence electron (8 maximum) • They don’t pair up until they have to (Hund’s rule) X

  9. The Electron Dot diagram for Nitrogen • Nitrogen has 5 valence electrons • First we write the symbol. N • Then add 1 electron at a time to each side. • Now they are forced to pair up. • We have now written the electron dot diagram for Nitrogen.

  10. The Octet Rule • Noble gases are unreactive in chemical reactions • 1916, Gilbert Lewis explain why atoms form certain kinds of ions and molecules • The Octet Rule: atoms tend to achieve noble gas configuration • Each noble gas (except He) has 8 electrons in the outer level

  11. Formation of Cations • Metals lose electrons to attain a noble gas configuration. • Make positive ions (cations) • Na 1s22s22p63s1 1 valence electron • Na1+1s22s22p6 This is a noble gas configuration with 8 electrons in the outer level.

  12. Electron Dots For Cations • Metals have few valence electrons (usually 3 or less); calcium has only 2 valence electrons Ca

  13. Electron Dots For Cations • Metals have few valence electrons • Metals will lose the valence electrons Ca

  14. Electron Dots For Cations • Metals have few valence electrons • Metals will lose the valence electrons • Forming positive ions Ca2+ This is named the calcium ion. NO DOTS are now shown for the cation.

  15. Electron Configurations: Anions • Nonmetals gain electrons to attain noble gas configuration. • Make negative ions (anions) • S = 1s22s22p63s23p4 = 6 valence electrons • S2- = 1s22s22p63s23p6 = noble gas configuration.

  16. Electron Dots For Anions • Nonmetals will have many valence electrons (usually 5 or more) • They will gain electrons to fill outer shell. P3- P This is called the phosphide ion

  17. Stable Electron Configurations • All atoms react to try and achieve a noble gas configuration. • Noble gases have 2 s and 6 p electrons. • 8 valence electrons = already stable! • This is the octet rule (8 in the outer level is particularly stable). Ar

  18. Section 7.2 Ionic Bonds and Ionic Compounds • OBJECTIVES: • Explain the electrical charge of an ionic compound.

  19. Section 7.2 Ionic Bonds and Ionic Compounds • OBJECTIVES: • Describe three properties of ionic compounds.

  20. Ionic Bonding • Anions and cations held together by opposite charges. • Ionic compounds = salts. • Simplest ratio = formula unit. • Held together by transfer of electrons. • Electrons are transferred to achieve noble gas configuration.

  21. Ionic Bonding Na Cl The metal (sodium) tends to lose its one electron from the outer level. The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.

  22. Ionic Bonding Na+ Cl - Note: Remember that NO DOTS are now shown for the cation!

  23. Ionic Bonding Lets do an example by combining calcium and phosphorus: • All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable). Ca P

  24. Ionic Bonding Ca P

  25. Ionic Bonding Ca2+ P

  26. Ionic Bonding Ca2+ P Ca

  27. Ionic Bonding Ca2+ P 3- Ca

  28. Ionic Bonding Ca2+ P 3- Ca P

  29. Ionic Bonding Ca2+ P 3- Ca2+ P

  30. Ionic Bonding Ca Ca2+ P 3- Ca2+ P

  31. Ionic Bonding Ca Ca2+ P 3- Ca2+ P

  32. Ionic Bonding Ca2+ Ca2+ P 3- Ca2+ P 3-

  33. Ionic Bonding = Ca3P2 Formula Unit This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance. For an ionic compound, the smallest representative particle is called a: Formula Unit

  34. Properties of Ionic Compounds • Crystalline solids - repeating arrangement of ions in the solid: Fig. 7.9, page 197 • Ions are strongly bonded together. • Structure is rigid. • High melting points • Coordination number- number of ions of opposite charge surrounding it

  35. - Page 198 Coordination Numbers: Both the sodium and chlorine have 6 NaCl Both the cesium and chlorine have 8 CsCl Each titanium has 6, and each oxygen has 3 TiO2

  36. Ionic Compound Model Project From Science Content Standards For California Schools Chemical Bonds 2c: Students know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction. Your assignment is to construct a model that demonstrates your mastery of the standard listed above. Your model will be scored according to the rubric at the bottom of this page.

  37. FAQ’s Q: Out of what shall I make my model? A: In the past, successful models have been made of marshmallows, toothpicks, Styrofoam balls, glue, clay, and marbles. You don’t need to go out and buy fancy Styrofoam balls to make this model. Q: I have a volleyball game this weekend. May I turn it my project in late? A: You may turn the project in the day after it is due for 50% maximum credit. Q: It’s Sunday night, and I didn’t read the chapter. Where is this in the book? A: Start reading on page 194 and continue through page 198. Q: May I work with a partner? A: Yes, if you are willing to split the points.

  38. Do they Conduct? • Conducting electricity means allowing charges to move. • In a solid, the ions are locked in place. • Ionic solids are insulators. • When melted, the ions can move around. • Melted ionic compounds conduct. • NaCl: must get to about 800 ºC. • Dissolved in water, they also conduct (free to move in aqueous solutions)

  39. - Page 198 The ions are free to move when they are molten (or in aqueous solution), and thus they are able to conduct the electric current.

  40. Section 7.3Bonding in Metals • OBJECTIVES: • Model the valence electrons of metal atoms.

  41. Section 7.3Bonding in Metals • OBJECTIVES: • Describe the arrangement of atoms in a metal.

  42. Section 7.3Bonding in Metals • OBJECTIVES: • Explain the importance of alloys.

  43. Metallic Bonds are… • How metal atoms are held together in the solid. • Metals hold on to their valence electrons very weakly. • Think of them as positive ions (cations) floating in a sea of electrons: Fig. 7.12, p.201

  44. + + + + + + + + + + + + Sea of Electrons • Electrons are free to move through the solid. • Metals conduct electricity.

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