Ionic bonds

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Ionic bonds

  1. 1. Ionic Bonds and Ionic Compounds
  2. 2. Chapter 4 Compounds and Their Bonds 4.1 Valence Electrons 4.2 Octet Rule and Ions LecturePLUS Timberlake 2
  3. 3. Chemical Bonds Attraction between two or more atoms Interaction between valence electrons Ionic bonds Covalent bonds LecturePLUS Timberlake 3
  4. 4. Valence Electrons Electrons in the highest (outer) electron level Have most contact with other atoms Known as valence electrons Outer shells of noble gases contain 8 valence electrons (except He = 2) Example: LecturePLUS Timberlake Ne 2, 8 Ar 2, 8, 8 4
  5. 5. Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons 1A 2A 3A 4A 5A 6A H 7A 8A He:  Li Be   B    C   Na Mg   Al  N     : F  :Ne : O      Si  P S         :Cl :Ar :    5
  6. 6. Learning Check  A. X would be the electron dot formula for 1) Na 2) K 3) Al  B.  X  would be the electron dot formula  1) B LecturePLUS Timberlake 2) N 3) P 6
  7. 7. Solution  A. X would be the electron dot formula for 1) Na 2) K  B.  X  would be the electron dot formula  2) N LecturePLUS Timberlake 3) P 7
  8. 8. Octet Rule  An octet in the outer shell makes atoms stable  Electrons are lost, gained or shared to form an octet  Unpaired valence electrons strongly influence bonding LecturePLUS Timberlake 8
  9. 9. Formation of Ions from Metals  Ionic compounds result when metals react with nonmetals  Metals lose electrons to match the number of valence electrons of their nearest noble gas  Positive ions form when the number of electrons are less than the number of protons Group 1A metals  ion 1+ Group 2A metals  ion 2+ • LecturePLUS Timberlake Group 3A metals  ion 3+ 9
  10. 10. Formation of Sodium Ion Sodium atom Na  2-8-1 Sodium ion – e  Na + 2-8 ( = Ne) 11 p+ 11 p+ 11 e- 10 e- 0 1+ 10
  11. 11. Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  2-8-2 – 2e  Mg2+ 2-8 (=Ne) 12 p+ 12 p+ 12 e- 10 e- 0 2+ 11
  12. 12. Some Typical Ions with Positive Charges (Cations) Group 1A Group 2A H+ Mg2+ Li+ Ca2+ Na+ Sr2+ K+ Group 3A Al3+ Ba2+ 12
  13. 13. Learning Check A. Number of valence electrons in aluminum 1) 1 e2) 2 e3) 3 eB. Change in electrons for octet 1) lose 3e2) gain 3 e3) gain 5 e- C. Ionic charge of aluminum 1) 32) 53) 3+ 13
  14. 14. Solution A. Number of valence electrons in aluminum 3) 3 eB. Change in electrons for octet 1) lose 3e- C. Ionic charge of aluminum 3) 3+ 14
  15. 15. Learning Check Give the ionic charge for each of the following: A. 12 p+ and 10 e1) 0 2) 2+ 3) 2- B. 50p+ and 46 e1) 2+ 2) 4+ 3) 4- C. 15 p+ and 18e2) 3+ LecturePLUS Timberlake 2) 3- 3) 515
  16. 16. Solution Give the ionic charge for each of the following: A. 12 p+ and 10 e2) 2+ B. 50p+ and 46 e2) 4+ C. 15 p+ and 18e2) 3LecturePLUS Timberlake 16
  17. 17. Learning Check A. Why does Ca form a Ca2+ ion? B. Why does O form O2- ion? LecturePLUS Timberlake 17
  18. 18. Solution A. Why does Ca form a Ca2+ ion? Loses 2 electrons to give octet 2-8-8-2 2-8-8 (like Ar) Why does O form O2- ion? B. Gains 2 electrons to give octet 2-6 LecturePLUS Timberlake + 2e- 2-8 (like Ne) 18
  19. 19. Ions from Nonmetal Ions In ionic compounds, nonmetals in 5A, 6A, and 7A gain electrons from metals Nonmetal add electrons to achieve the octet arrangement Nonmetal ionic charge: 3-, 2-, or 1- 19
  20. 20. Fluoride Ion unpaired electron  :F  2-7 9 p+ 9 e0 LecturePLUS Timberlake octet  + e 1- : F:  2-8 (= Ne) 9 p+ 10 e1ionic charge 20
  21. 21. Learning Check Complete the names of the following ions: 5A N3 nitride P3 ___________ 6A O2 __________ S2 __________ 7A F fluoride Cl _________ Br  _________ LecturePLUS Timberlake 21
  22. 22. Solution 5A 6A 7A N3 O2 F nitride oxide P3 S2 Cl phosphide sulfide chloride fluoride Br  bromide LecturePLUS Timberlake 22

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