1. M. I. T. CHEMISTRY Introduction to Octet Rule

4. The nucleus is a solid core, and that core is covered by shells of electrons. Just as the outside layer of an onion is the only one that goes brown, so it is only the outer shell of an atom that reacts with other atoms. Atoms can be viewed as onions.

5. The number of electrons in an atom’s outer shell. PERIODIC TABLE GROUPOUTER ELECTRONS GROUP 1: Alkali Metals1 GROUP 2: Alkali Earth Metals2 GROUP 3-12: Transition MetalsVaries GROUP 13: Boron Group3 GROUP 14: Carbon Group4 GROUP 15: Nitrogen Group5 GROUP 16: Chalcogens6 GROUP 17: Halogens7 GROUP 18: Noble Gases8

6. Valence Electrons The number of electrons gained, lost or shared. PERIODIC TABLE GROUPOUTER ELECTRONS GROUP 1: Alkali Metals1 GROUP 2: Alkali Earth Metals2 GROUP 3-12: Transition MetalsVaries GROUP 13: Boron Group3 GROUP 14: Carbon Group4 GROUP 15: Nitrogen Group3 GROUP 16: Chalcogens2 GROUP 17: Halogens1 GROUP 18: Noble Gases0

7. The “Filling Pattern” The pattern is 2, 8, 8, 2 for the first four shells. It is important to realize that this only applies for the first 20 elements.

8. Octet Rule Atoms tend to gain, lose or share one or more of their valence electrons to achieve a complete octet of 8 valence electrons. Negative ions are formed when an element gains electrons. Positive ions are formed when an element gains electrons. 8 is Great!

9. Lewis Dot Diagram An element’s chemical symbol is surrounded by a # of dots corresponding to the # of valence electrons.

10. Only the valence electrons are diagrammed.

11. Only the valence electrons are diagrammed.

12. Lewis Dot Diagram Only the valence electrons are diagrammed.

13. Lewis Dot Diagram Only the valence electrons are diagrammed.

15. Lewis Dot Diagram Only the valence electrons are diagrammed.

16. Compound Lewis Dot Diagramming Compounds Containing 2 Atoms. Hydrogen Fluoride Draw the Lewis Dot diagram for each element. Place the diagrams together.

17. Compounds Containing More Than 2 Atoms Nitrogen Trifluoride Step 1: Determine the number of valence electrons available. N = 5 3F = 21 Total = 26

18. Compounds Containing More Than 2 Atoms Nitrogen Trifluoride Step 2: Determine the number of electrons needed to satisfy the octet rule. N = 8 3F = 24 Total = 32

19. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Nitrogen Trifluoride Step 3: Determine the difference between steps 1 & 2. Step 1 = 26 Step 2 = 32 Electrons to be shared = 6

20. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Nitrogen Trifluoride Step 4: Place the atoms as symmetrically as possible.

21. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Nitrogen Trifluoride Step 5: Place the number of electrons to be shared between the atoms, a pair at a time.

22. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Nitrogen Trifluoride Step 6: Add the remainder of the available electrons.

23. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Sulfur Dioxide Step 1: Determine the number of valence electrons available.

24. Compounds Containing More Than 2 Atoms Sulfur Dioxide Step 2: Determine the number of electrons needed to satisfy the octet rule.

25. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Sulfur Dioxide Step 3: Determine the difference between steps 1 & 2.

26. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Sulfur Dioxide Step 4: Place the atoms as symmetrically as possible.

27. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Sulfur Dioxide Step 5: Place the number of electrons to be shared between the atoms, a pair at a time.

28. Compound Lewis Dot Diagramming Compounds Containing More Than 2 Atoms Sulfur Dioxide Step 6: Add the remainder of the available electrons.

29. Lewis Dot Diagramming Worksheet Row 1 H 2 HCl F 2 O 2

30. Row 2 CO 2 CH 2 O CO H 2 S

31. Row 3 CHCl 3 NF 3 SiCl 4 AlH 3

32. Row 4 PH 3 CS 2 CCl 4 H 3 O+

33. Row 5 NH 4 + BrO 3 - NO 3 - SO 4 2+