1 Compounds and Their Bonds Octet Rule and Ions Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Valence electrons: The electrons in the outer most shell. Usually, to show electrons, we draw dots around the symbol for an atom. These are known as “Lewis Dot Diagrams”. HINT! The number of Valence Electrons an atom has, is the same as it’s Group Number! Valence Electrons

3 Let’s practice with an element. -Step 1: Look at the group number to find out how many valence electrons an atom has. -Step 2: Draw the valence electrons in a dot diagram around the Element. -Practice with Mg Octet Rule

4 Let’s practice with an element. -Step 1: Look at the group number to find out how many valence electrons an atom has. -Step 2: Draw the valence electrons in a dot diagram around the Element. -Mg is in the 2 nd Group, meaning it has 2 electrons in the valence shell. -The Lewis Dot Diagram would look like Mg: Octet Rule

5 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

6 Ionic and Covalent Bonds Atoms form octets to become more stable. by losing, gaining, or sharing valence electrons. by forming ionic bonds or covalent bonds. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings :

7 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 © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

8 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+.

9 Formation of Negative Ions In ionic compounds, nonmetals achieve an octet arrangement. gain electrons. form negatively charged ions with 3-, 2-, or 1- charges.

10 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-