2. IONIC AND METALLIC BONDS

3. Why do bonds form? Lesson Essential Question:

4. Valence Electrons:  Valence electrons = outermost electrons Neon: 1s 2 2s 2 2p 6 Argon: 1s 2 2s 2 2p 6 3s 2 3p 6 Krypton: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 Barium: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 Notice that the outermost sublevels are S and P orbitals!

5. Stability  Electron configurations are most stable when the s and p orbitals are completely filled.  This is called the octet rule.  Electrons are traded and shared in order to achieve stable electron configurations.  In this way, valence electrons predict how an atom is likely to interact (or react) with other atoms.  Valence electrons determine bonding patterns.

6. Electron Dot diagrams…  valence e-’s  symbol represents nucleus & core e-’s  Each side = orbital (s or p)  dot = valence e- (8 max)  don’t pair up until they have to (Hund’s rule) X (s) (p x ) (p z ) (p y )

7. Atoms in the same column... 1) same outer e- configuration 2) same valence e-’s  valence e-’s easily determined  equal to group # for representative element 2A: Be, Mg, Ca, etc. have 2 valence e-’s

8. Electron Dot Structures

9. Electron Dots For Cations  Metals few valence e-’s  Metals lose Ca

10. Electron Dots For Cations  Form + ions Ca 2+ NO DOTS shown for cation “calcium ion”. This is named the “calcium ion”.

11. Electron Dots For Anions  Nonmetals have many valence e-’s (usually 5+)  gain e-’s P 3- (called “phosphide ion”, and should show dots)

12. Stable Electron Configurations  All atoms react to achieve NGC  Noble gases… s 2 p 6  8 valence e-’s (stable)  octet rule Ar Electron dot activity

13. Why bond?  Bonding enables atoms to achieve stable electron configurations.

14. What are ions? How do ionic compounds form? Lesson Essential Question:

15. Ions  Cation: positive due to e- loss  Anion: negative due to e- gain Ions are most stable when they have the electron configurations of noble gases (full s and p orbitals)

16. Ionic compounds  Ionic compounds are formed by a transfer of electrons  when a cation and an anion are associated by attraction  Formula unit = simplest ratio of elements in an ionic compound

17. Ionic Bonding Na Cl metal (sodium) loses one valence e- Cl needs 1 e- for octet

18. Ionic Bonding Na + Cl - NOTE: NO DOTS shown for cation

19. Ionic Bonding  All e-’s must be accounted for,  each atom has NGC (stable) CaP combining calcium and phosphorus:

20. Ionic Bonding CaP

21. Ionic Bonding Ca 2+ P

22. Ionic Bonding Ca 2+ P Ca

23. Ionic Bonding Ca 2+ P 3- Ca

24. Ionic Bonding Ca 2+ P 3- Ca P

25. Ionic Bonding Ca 2+ P 3- Ca 2+ P

26. Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

27. Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

28. Ionic Bonding = Ca 3 P 2 Formula Unit chemical formula - shows kinds and numbers of atoms in smallest representative particle of substance. Formula Unit - smallest representative particle in ionic cmpd

29. Properties of Ionic Compounds 1. Crystalline solids - regular repeating arrangement of ions in the solid: Fig. 7.9, page 197  Ions strongly bonded  Rigid structure 2. High melting points  Coordination number- # of ions of opposite charge surrounding it Chemistry of salt 6:23

30. - Page 198 Coordination Numbers: Both the sodium and chlorine have 6 Maximizes contact btwn opp charges Both the cesium and chlorine have 8 Each titanium has 6, and each oxygen has 3 NaCl CsCl TiO 2

31. Do they Conduct? 3. Melted ionic cmpds conduct  Crystal structure breaks down  ions free to move (molten or aqueous)

32. How does metallic bonding affect the properties of metals? Lesson Essential Question:

33. Electrons in Metals  Metals hold on to their valence electrons weakly  Cations in a sea of electrons

34. Properties of Metals  Conduct electricity (electrons flowing between)  Maleable  Ductile  Luster

35. Malleable ++++ ++++ ++++ Force

36. Malleable  Mobile e-’s allow atoms to slide by  like ball bearings in oil. ++++ ++++ ++++ Force

37. Ionic solids are brittle +-+- + - +- +-+- + - +- Force

38. Ionic solids are brittle  Strong Repulsion breaks crystal apart, b/c similar ions next to each other. + - + - + - +- +-+- + - +- Force

39. Alloys  We use metals every day, few pure metals  Alloys made by melting a mixture of ingredients, then cooling  Brass: alloy of Cu and Zn  Bronze: Cu and Sn

40. Alloys