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Chapter 15

Chapter 15. Ionic Bonding. Keeping Track of Electrons. The electrons responsible for the chemical properties of atoms are those in the outer energy level. Valence electrons - The s and p electrons in the outer energy level. Core electrons -those in the energy levels below. .

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Chapter 15

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  1. Chapter 15 Ionic Bonding

  2. Keeping Track of Electrons • The electrons responsible for the chemical properties of atoms are those in the outer energy level. • Valence electrons - The s and p electrons in the outer energy level. • Core electrons -those in the energy levels below.

  3. Keeping Track of Electrons • Atoms in the same column • Have the same outer electron configuration. • Have the same valence electrons. • Easily found by looking up the group number on the periodic table. • Group 2A - Be, Mg, Ca, etc.- • 2 valence electrons

  4. Electron Dot diagrams • A way of keeping track of valence electrons. • How to write them • Write the symbol. • Put one dot for each valence electron • Don’t pair up until they have to X

  5. 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. • Until they are forced to pair up.

  6. Write the electron dot diagram for • Na • Mg • C • O • F • Ne • He

  7. Electron Configurations for Cations • Metals lose electrons to attain noble gas configuration. • They make positive ions. • If we look at electron configuration it makes sense. • Na 1s22s22p63s1 - 1 valence electron • Na+ 1s22s22p6 -noble gas configuration

  8. Electron Dots For Cations • Metals will have few valence electrons Ca

  9. Electron Dots For Cations • Metals will have few valence electrons • These will come off Ca

  10. Electron Dots For Cations • Metals will have few valence electrons • These will come off • Forming positive ions Ca+2

  11. Electron Configurations for Anions • Nonmetals gain electrons to attain noble gas configuration. • They make negative ions. • If we look at electron configuration it makes sense. • S 1s22s22p63s23p4 - 6 valence electrons • S-2 1s22s22p63s23p6 -noble gas configuration.

  12. Electron Dots For Anions • Nonmetals will have many valence .electrons. • They will gain electrons to fill outer shell. P P-3

  13. Stable Electron Configurations • All atoms react to achieve noble gas configuration. • Noble gases have 2 s and 6 p electrons. • 8 valence electrons . • Also called the octet rule. Ar

  14. Ionic Bonding • Anions and cations are held together by opposite charges. • Ionic compounds are called salts. • Simplest ratio is called the formula unit. • The bond is formed through the transfer of electrons. • Electrons are transferred to achieve noble gas configuration.

  15. Ionic Bonding Na Cl

  16. Ionic Bonding Na+ Cl-

  17. Ionic Bonding • All the electrons must be accounted for! Ca P

  18. Ionic Bonding Ca P

  19. Ionic Bonding Ca+2 P

  20. Ionic Bonding Ca+2 P Ca

  21. Ionic Bonding Ca+2 P-3 Ca

  22. Ionic Bonding Ca+2 P-3 Ca P

  23. Ionic Bonding Ca+2 P-3 Ca+2 P

  24. Ionic Bonding Ca Ca+2 P-3 Ca+2 P

  25. Ionic Bonding Ca Ca+2 P-3 Ca+2 P

  26. Ionic Bonding Ca+2 Ca+2 P-3 Ca+2 P-3

  27. Ionic Bonding Ca3P2 Formula Unit

  28. Properties of Ionic Compounds • Crystalline structure. • A regular repeating arrangement of ions in the solid. • Ions are strongly bonded. • Structure is rigid. • High melting points- because of strong forces between ions.

  29. Crystalline structure

  30. Do they Conduct? • Conducting electricity is 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. • First get them to 800ºC. • Dissolved in water they conduct.

  31. Metallic Bonds • How atoms are held together in the solid. • Metals hold onto their valence electrons very weakly. • Think of them as positive ions floating in a sea of electrons.

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

  33. Metallic Bonding

  34. Metals are Malleable • Hammered into shape (bend). • Ductile - drawn into wires.

  35. Alloys • Mixture of metal atoms • Can have properties different than individual metals • Examples: brass, aluminum alloys used in cars

  36. + + + + + + + + + + + + Malleable

  37. + + + + + + + + + + + + Malleable • Electrons allow atoms to slide by.

  38. + - + - - + - + + - + - - + - + Ionic solids are brittle

  39. - + - + - + - + + - + - - + - + Ionic solids are brittle • Strong Repulsion breaks crystal apart.

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