1 Chapter 3 Electronic Structure and Periodic Law 3.3 The Shell Model and Chemical Properties Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Valence Electrons or Shell The valence electrons or valence shells determine the chemical properties of the elements. are the electrons in the highest energy level. are related to the group number of the element. Example: Phosphorus has 5 valence electrons. 5 valence electrons P Group 5A(15) 2, 8, 5

3 All the elements in a group have the same number of valence electrons. Example: Elements in group 2A(2) have two (2) valence electrons. Be2, 2 Mg 2, 8, 2 Ca 2, 8, 8, 2 Sr 2, 8, 18, 8, 2 Groups and Valence Electrons

4 Periodic Table and Valence Electrons Representative Elements Group Numbers H He 1 2 Li Be Al C N O F Ne 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 Li Mg Ge Si P S Cl Ar 2,8,1 2,8,2 2,8,3 2,8,4 2,8,5 2,8,6 2,8,7 2,8,8

6 State the number of valence electrons for each. A. O 1) 42) 63) 8 B. Al 1) 132) 33) 1 C. Cl 1) 22) 53) 7 Learning Check

7 State the number of valence electrons for each. A. O 2) 6 B. Al 2) 3 C. Cl 3) 7 Solution

8 State the number of valence electrons for each. A. calcium 1) 12) 23) 3 B. group 6A (16) 1) 22) 43) 6 C. tin 1) 22) 43) 14 Learning Check

9 State the number of valence electrons for each. A. calcium 2) 2 B. group 6A (16) 3) 6 C. tin 2) 4 Solution

10 State the number of valence electrons for each. A. 2, 8, 5 B. 2, 8, 8, 2 C. 2, 7 Learning Check

11 State the number of valence electrons for each. A. 2, 8, 55 B. 2, 8, 8, 22 C. 2, 77 Solution