How Atoms Bond

1. How Atoms Bond Chapter 17

2. Let’s Review

4. Electrons are arranged in energy levels

5. Electrons are arranged in energy levels

6. Electrons are arranged in energy levels

7. Take a Look at Helium

8. The Language of Chemistry CHEMICAL ELEMENTS -pure substances that cannot be decomposed by ordinary means to other substances

9. Symbols of Elements • Use 1 or 2 letter abbreviations • Capitalize the first letter only • Examples • C Carbon Co Cobalt • N Nitrogen Ca Calcium • F Fluorine Br Bromine • O Oxygen Mg Magnesium

10. The Periodic Table Dimitri Mendeleev 1834-1907

11. The Periodic Table Helium 2 Atomic Number He e P P N N e 4.003 Atomic Mass Atomic mass 4 amu

12. The Periodic Table Helium 2 Atomic Number He e P P N N e 4.003 Atomic Mass Atomic mass 4 amu

13. The way the table is organized tells a lot about the elements’ properties

14. Now… let’s combine all this information

15. …and watch what happens!

16. …and watch what happens!

17. You’ve built this in class!

18. The electrons in the outer rings are called “valence electrons”

19. Valence electrons play an important role an element’s ability to form chemical bonds (chemical properties).

20. How many e- are in the outer rings? Do you see the valence patterns? Valence Electrons 1 e- 2 e- 3 e- 4 e- 5 e- 6 e- 7 e- 8 e-

21. Gilbert Newton Lewis 1875-1946 • Chemist at UC Berkeley • Exceptional teacher • Productive researcher • “Theory of Chemical Bonding” • Lewis Dot Structures

22. Lewis Dot Structures • Convenient • Easy way to understand chemical bonding

23. Dot structures simplify this information Valence Electrons 1 e- 2 e- 3 e- 4 e- 5 e- 6 e- 7 e- 8 e-

24. Dot structures only use the valence electrons Valence Electrons 1 e- 2 e- 3 e- 4 e- 5 e- 6 e- 7 e- 8 e-

25. Watch…. H Li Valence Electrons Valence Electrons 1 e- 1 e-

26. Try this…. Na Valence Electrons Valence Electrons 1 e- 1 e-

27. Look at Group 2…. Mg Be Valence Electrons Valence Electrons 2 e- 2 e-

28. Group I3…. B Al ? Valence Electrons Valence Electrons 3 e- 3 e-

29. Group I4…. C Si Silicon Valence Electrons Valence Electrons 4 e- 4 e-

30. Group 15…. N P Phosphorous Valence Electrons Valence Electrons 5 e- 5 e-

31. Group 16…. O S Valence Electrons Valence Electrons 6 e- 6 e-

32. Group 17…. Cl F Valence Electrons Valence Electrons 7 e- 7 e-

33. Group 18…. Ne He Valence Electrons Valence Electrons 8 e- 8 e-

35. Chemical Bonds • Atoms can gain, lose or share electrons. • Forces holding these atoms together are known as chemical bonds

36. Chemical Bonds • Attraction between 2 or more atoms • Interaction between valence electrons Ionic Bonds Covalent Bonds

37. Electrons in the highest (outer) level Have most contact with other atoms Known as valence electrons Outer shells of noble gases contain 8 valence electrons (except, He = 2) Valence Electrons Helium Neon Argon

38. Octet Rule So… Chemical bonds are formed when atoms try to fill their outer electron shell and obey the octet rule.

39. Attraction between oppositely charged ions Ionic Bonds

43. Using Lewis Dot Structures

44. Predicting Ionic Bonds

45. Salt

47. Covalent bonds form molecules

48. Double Covalent bonds