1. Why are electrons important? Electrons are responsible for HOW ELEMENTS REACT That is why we learned how to: – Write electron configurations – Draw electron orbital diagrams When we understand electrons – we can predict how elements will behave (what we can do with them) – Understand the structure of the periodic table

2. Valence Electrons The specific electrons responsible for the chemical properties of an element Electrons in an atoms outermost orbitals They are in the highest energy levels

3. Valence Electrons Identify number of valence electrons using… – Electron Shell Diagrams – Electron Configurations – Periodic Table

4. Electron Shell Diagrams Electron Shell Diagram Element Symbol FClBrI # Protons # Total Electrons # Valence Electrons 9 9 7 17 7 35 7 53 7

5. Electron Shell Diagrams Rules – Draw the nucleus (label number of protons) – Determine number of total electrons – The 1 st shell can only hold 2 electrons – The 2 nd and 3 rd shells can only hold 8 electrons 9 Fluorine 9 protons 9 electrons

6. Electron Shell Diagrams Electron Shell Diagram Element Symbol B # Protons # Total Electrons # Valence Electrons 5 5 5 3

7. Electron Shell Diagrams Electron Shell Diagram Element Symbol C # Protons # Total Electrons # Valence Electrons 6 6 6 4

8. Electron Shell Diagrams Electron Shell Diagram Element Symbol N # Protons # Total Electrons # Valence Electrons 7 7 7 5

9. Electron Shell Diagrams Electron Shell Diagram Element Symbol O # Protons # Total Electrons # Valence Electrons 8 8 8 6

10. Electron Configuration 1. Write the electron configuration O1s 2 2s 2 2p 4 2. Circle the subshells in the highest energy levels O1s 2 2s 2 2p 4 3. Count the electrons in those orbitals O1s 2 2s 2 2p 4 24 + = 6 O

11. Electron Configuration Element Symbol Electron Configuration # Total Electrons # Valence Electrons Li 1s 2 2s 1 31 Be 1s 2 2s 2 42 Si 1s 2 2s 2 2p 6 3s 2 3p 2 144 Na1s 2 2s 2 2p 6 3s 1 111 Al1s 2 2s 2 2p 6 3s 2 3p 1 133 S1s 2 2s 2 2p 6 3s 2 3p 4 166

12. Periodic Table 7 7 7 7 3 4 56 1 2 4 13 6 The number of valence electrons is the same for all elements in a group (column).

13. Lewis Dot Structures 1.Determine the _______________ _______________________ for the element. 2.Write the element’s ___________. number of valence electrons symbol

14. Lewis Dot Structures 3.Draw _____________________ around the symbol. a.Add a _______ _ dot to the _______ side of the symbol. b.Continue adding _________ dots _____________ around the symbol. c.Pair up dots only when _______________ of the symbol has a single dot. valence electrons singleright single clockwise all 4 sides

15. Lewis Dot Structures 1.Determine the number of valence electrons for the element. 2.Write the element’s symbol. 3.Draw valence electrons around the symbol. Mg Magnesium 2 valence electrons

16. Lewis Dot Structures 1.Determine the number of valence electrons for the element. 2.Write the element’s symbol. 3.Draw valence electrons around the symbol. Cl Chlorine 7 valence electrons

17. Element Lithium # Valence electrons 1 Lewis dot structure Li Lewis Dot Structures

18. Element Magnesium # Valence electrons 2 Lewis dot structure Mg Lewis Dot Structures

19. Element Boron # Valence electrons 3 Lewis dot structure B Lewis Dot Structures

20. Element Silicon # Valence electrons 4 Lewis dot structure Si Lewis Dot Structures

21. Element Nitrogen # Valence electrons 5 Lewis dot structure N Lewis Dot Structures

22. Element Oxygen # Valence electrons 6 Lewis dot structure O Lewis Dot Structures

23. Element Chlorine # Valence electrons 7 Lewis dot structure Cl Lewis Dot Structures

24. Element Neon # Valence electrons 8 Lewis dot structure Ne Lewis Dot Structures