1 Chapter 5 Ionic Compounds 5.1 Octet Rule and Ions Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 An octet Contains 8 valence electrons. Is associated with the stability of the noble gases. Exception is He that is stable with 2 valence electrons (duet). valence electrons He 22 Ne 2, 88 Ar 2, 8, 8 8 Kr 2, 8, 18, 88 Octet Rule

3 Forming Octets Atoms acquire octets By forming compounds. To become more stable. By losing, gaining, or sharing valence electrons. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

4 Ionic and Covalent Bonds Ionic bonds involve Loss of electrons by a metal. Gain of electrons by a nonmetal. Covalent bonds involve A sharing of electrons. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

5 Metals Form Positive Ions Metals form Octets by losing all of their valence electrons. Positive ions with the electron configuration of the nearest noble gas. Positive ions with fewer electrons than protons. Group 1A(1) metals  ion 1+ Group 2A(2) metals  ion 2+ Group 3A(13) metals  ion 3+ Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

6 Formation of a Sodium Ion, Na + Sodium achieves an octet by losing its one valence electron. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings 2, 8, 1 2, 8

7 Charge of Sodium Ion, Na + With the loss of its valence electron, the sodium ion has a 1+ charge. Sodium atom Sodium ion 11p + 11e - 10e Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings 2, 8

8 Formation of Mg 2+ Magnesium achieves an octet by losing its two valence electrons. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings 2, 8, 2 2, 8

9 Charge of Magnesium Ion Mg 2+ With the loss of two valence Electrons, magnesium forms a positive ion with a 2+ charge. Mg atomMg 2+ ion 12p + 12p + 12e- 10e Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings 2, 8

10 Learning Check Select the correct answer for aluminum: A. Number of valence electrons 1) 1e - 2) 2e - 3) 3e - B. Electron change for octet 1) loss of 3e - 2) gain of 3e - 3) gain of 5e - C. Ionic charge of aluminum ion 1) 3-2) 5- 3) 3 + D. The symbol for the aluminum ion 1) Al 3+ 2) Al 3- 3) Al +

11 Solution Select the correct answer for aluminum: A. Number of valence electrons 3) 3e - B. Electron change for octet 1) loss of 3e - C. Ionic charge of aluminum ion 3) 3 + D. The symbol for the aluminum ion 1) Al 3+

12 Formation of Negative Ions In ionic compounds, nonmetals Achieve an octet arrangement. Gain electrons. Form negatively charged ions with 3-, 2-, or 1- charges.

13 Formation of Chloride Ion, Cl - Chlorine achieves an octet by adding an electron to its valence electrons. Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings 2, 8, 7 2, 8, 8

14 Charge of a Chloride Ion, Cl - A chlorine ion forms When Cl gains one electron With a 1- charge. Chlorine atom Chloride ion 17p + 17p + 17e - 18e – Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

15 Some Ionic Charges Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

16 Select the correct answer for sulfur A. Number of valence electrons 1) 4e - 2) 6e - 3) 8e - B. Change in electrons for octet 1) loss of 2e - 2) gain of 2e - 3) gain of 4e - C. Ionic charge of sulfide ion 1) 2+ 2) 2- 3) 4- Learning Check

17 Select the correct answer for sulfur A. Number of valence electrons 2) 6e - B. Change in electrons for octet 2) gain of 2e - C. Ionic charge of sulfide ion 2) 2- Solution

18 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(13) = 3+ The charge of a negative ion is obtained by subtracting 8 or 18 from its Group number. Group 6A(16) = = 2- or = 2-