1 Chapter 4 Compounds and Their Bonds 4.1 Octet Rule and Ions Copyright © 2009 by Pearson Education, Inc.

2 An octet is 8 valence electrons. is associated with the stability of the noble gases. He is stable with 2 valence electrons (duet). valence electrons He 2 2 Ne 2, 8 8 Ar 2, 8, 8 8 Kr 2, 8, 14, 8 8 Octet Rule

3 Ionic and Covalent Bonds Atoms that are not noble gases form octets to become more stable. by losing, gaining, or sharing valence electrons. by forming ionic bonds or covalent bonds.

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 metals ion 1+ Group 2A metals ion 2+ Group 3A metals ion 3+ Copyright © 2009 by Pearson Education, Inc.

5 Formation of a Sodium Ion, Na +

6 Charge of Sodium Ion, Na + With the loss of its valence electron, the sodium ion has a 1+ charge. Na atom Na + ion 11p + 11e - 10e , 8 Copyright © 2009 by Pearson Education, Inc.

7 Formation of Mg 2+ Magnesium achieves an octet by losing its two valence electrons.

8 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 © 2009 by Pearson Education, Inc.

9 Learning Check A. The number of valence electrons in aluminum is 1) 1e -. 2) 2e -.3) 3e -. B. The change in electrons for octet requires a 1) loss of 3e -. 2) 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 Solution A. The number of valence electrons in aluminum is 3) 3 e -. B. The change in electrons for octet requires a 1) loss of 3e -. C. The ionic charge of aluminum is 3) 3+. D. The symbol for the aluminum ion is 1) Al 3+.

11 Formation of Negative Ions In ionic compounds, nonmetals in Groups 5A (15), 6A (16) and 7A (17) achieve an octet arrangement by gaining electrons. form negatively charged ions with 3-, 2-, or 1- charges.

12 Formation of a Chloride, Cl - Chlorine achieves an octet by adding an electron to its valence electrons.

13 Charge of a Chloride Ion, Cl - By gaining 1 electron, the chloride ion has a 1- charge. Chlorine atom, Cl Chloride ion, Cl – 17p + 17p + 17e - 18e – Copyright © 2009 by 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) = = 2- or = 2-

15 Some Ionic Charges

16 A. The number of valence electrons in sulfur is 1) 4e -. 2) 6e -. 3) 8e -. B. The change in electrons for octet requires a 1) loss of 2e -. 2) gain of 2e -. 3) a gain of 4e -. C. The ionic charge of sulfur is 1) 2+. 2) 2-. 3) 4-. Learning Check

17 A. The number of valence electrons in sulfur is 2) 6e -. B. The change in electrons for octet requires a 2) gain of 2e -. C. The ionic charge of sulfur is 2) 2-. Solution