1. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 1 Chapter 5 Compounds and Their Bonds 5.1 Octet Rule and Ions

2. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 2 An octet  is 8 valence electrons  is associated with the stability of the noble gases  does not occur with He; He is stable with 2 valence electrons (duet) Valence Electrons He 1s 2 2 Ne 1s 2 2s 2 2p 6 8 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 8 Kr 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 8 Octet Rule

3. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 3 Ionic and Covalent Bonds Atoms form octets  to become more stable  by losing, gaining, or sharing valence electrons  by forming ionic or covalent bonds

4. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 4 Metals Form Positive Ions Metals form positive ions  by a loss of their valence electrons  with the electron configuration of the nearest noble gas  that have fewer electrons than protons Group 1A(1) metals ion 1+ Group 2A(2) metals ion 2+ Group 3A(3) metalsion 3+

5. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 5 Formation of a Sodium Ion, Na + Sodium achieves an octet by losing its one valence electron.

6. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 6 Charge of Sodium Ion, Na + With the loss of its valence electron, a sodium ion has a 1 + charge. Sodium atom Sodium ion 11p + 11e – 10e – 0 1 +

7. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 7 Formation of Magnesium Ion, Mg 2+ Magnesium achieves an octet by losing its two valence electrons.

8. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 8 Charge of Magnesium Ion, Mg 2+ With the loss of two valence electrons magnesium forms a positive ion with a 2 + charge. Mg atom Mg 2+ ion 12p + 12p + 12e – 10e – 0 2 +

9. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 9 Learning Check A. The number of valence electrons in aluminum is 1) 1e – 2) 2e – 3) 3e – B. To acquire an octet of electrons in aluminum requires 1) a loss of 3e – 2) a gain of 3e – 3) a gain of 5e – C.The ionic charge of aluminum is 1) 3 – 2) 5 – 3) 3 + D. The symbol for the aluminum ion is 1) Al 3+ 2) Al 3– 3) Al +

10. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 10 Solution A. The number of valence electrons in aluminum is 3) 3 e – B. To acquire an octet of electrons in aluminum requires 1) a loss of 3e – C. The ionic charge of aluminum is 3) 3 + D. The symbol for the aluminum ion is 1) Al 3+

11. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 11 Formation of Negative Ions In ionic compounds, nonmetals  achieve an octet arrangement  gain electrons  form negatively charged ions with 3 –, 2 –, or 1 – charges

12. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 12 Formation of a Chloride Ion, Cl – Chlorine achieves an octet by adding an electron to its valence electrons.

13. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 13 Charge of a Chloride Ion, Cl –  By gaining one electron, the chloride ion has a – 1 charge. Chlorine atom Chloride ion 17p + 17p + 17e – 18e – 0 1 –

14. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 14 Ionic Charge from Group Numbers  The charge of a positive ion is equal to its Group number. Group 1A(1) = 1 + Group 2A(2) = 2 + Group 3A(3) = 3 +  The charge of a negative ion is obtained by subtracting 8 or 18 from its Group number. Group 6A(16) = 6 – 8 = 2 – or 16 – 18= 2 –

15. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 15 Some Typical Ionic Charges

16. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Group Number and Ionic Charge Ions  achieve the electron configuration of their nearest noble gas  of metals in Groups 1A(1), 2A(2), or 3A(13) have positive 1 +, 2 +, or 3 + charge.  Of nonmetals in Groups 5A(15), 6A(16), or 7A(17) have negative 3 –, 2 –, or 1 – charge. 16

17. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Groups Numbers for Some Positive and Negative Ions 17

18. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 18 A. The Group number for sulfur is 1) 4A(14) 2) 8A(18) 3) 6A(16) B. The number of valence electrons in sulfur is 1) 4e  2) 6e  3) 8e  C. The change in electrons for an octet requires a 1) gain of 2e  2) loss of 2e  3) a gain of 4e  D. The ionic charge of sulfur is 1) 2 + 2) 2  3) 4  Learning Check

19. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 19 A. The Group number for sulfur is 3) 6A(16) B. The number of valence electrons in sulfur is 2) 6e  C. The change in electrons for octet requires a 1) gain of 2e  D. The ionic charge of sulfur is 2) 2  Solution

20. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Sizes of Atoms and Their Ions Metals  lose their valence electrons  form ions that are smaller than their atoms Nonmetals (in ionic compounds)  gain valence electrons  form ions that are larger than their atoms 20

21. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Metal Ions are Smaller 21 In Group 1A(1), the ions are smaller than their corresponding atoms.

22. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. Nonmetal Ions are Larger 22 In Group 7A(17), the ions are larger than their corresponding atoms.

23. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 23 Select the larger atom or ion in the following: 1. Mg or Mg 2+ 2. S or S 2  3. Br or Br  Learning Check

24. General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 24 Select the larger atom or ion in the following: 1. Mg or Mg 2+ Mg 2. S or S 2  S 2  3. Br or Br  Br  Solution