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6. Types of Bonding
Ionic
Covalent
Metallic
Van der Waals (Secondary)

7. The Periodic Table Columns: Similar Valence Structure give up 1e-
inert gases
accept 1e-
accept 2e- O Se Te Po At I Br He Ne Ar Kr Xe Rn F Cl S Li Be H Na Mg Ba Cs Ra Fr Ca K Sc Sr Rb Y
Columns: Similar Valence Structure
Electronegative elements:
Readily acquire electrons
to become - ions.
Electropositive elements:
Readily give up electrons
to become + ions.
Adapted from Fig. 2.6, Callister & Rethwisch 8e. 7

8. Rule #2: Stable Configurations
Some electron configurations
are especially stable.
(Think “noble gases”)

9. f06_02_pg23
Example: Na, Cl
f06_02_pg23.jpg

10. Rule #1: Electrical Neutrality
Opposites attract

11. 1) Ionic Bonding Atoms take/give electrons to neighbor
Often 1 metallic & 1 non-metallic
(Elements from opposite sides of table)

12. 2) Covalent bonding
Atoms Share Electrons

13. f06_02_pg23
Example: H2O
f06_02_pg23.jpg

14. 2) Covalent bonding
Adjacent atoms share electrons to achieve stable e- configuration

15. Reality check ionic covalent Nature of the bond reported as:
Percent ionic character

16. 3) Metallic Bonding Share electrons (“sea of electrons”)
Orbitals never completely filled: Electrons jump from atom to atom

17. Secondary or Van der Waals Bonding
Section 2.7
Secondary or Van der Waals Bonding

18. Rule #3: Dipoles almost always occur

19. 4) Secondary (Van der Waals) bonding
Weak compared to primary bonds
Can significantly affect material properties

20. 4) Secondary (Van der Waals) bonding
Fluctuating induced dipole moments
Before:
Ion
core
Ion
core –
Ion
core +
After: –
Ion
core + –

21. 4) Secondary (Van der Waals) bonding
Permanent Dipole Bonds
Permanent dipole moments in the molecule.
Bonds stronger than for Fluctuating
Example: H2O H H H – O + – O + – O + H H H

22. For which will VdW forces have the strongest influence on properties?
Covalent bond: Where a rod meets a ball A.
Graphite
(Carbon) B.
Diamond
(Carbon)

23. Structure of Crystalline Solids
Sections 3.1–3.4; 3.7
Structure of Crystalline Solids

24. Cubic xl Structures

25. Unit Cell
Smallest structural unit that generates a 3-D xl (if repeated).
7 Crystal Systems—Only 7 unit cell shapes for all xl structures.

26. Crystal Systems
Table 3.2

27. Crystal Systems, cont’d
Table 3.2, cont’d

28. Unit cell f04_03_pg46 Cubic System a = b = c a = b = g = 90º Fig. 3.4
f04_03_pg46.jpg
Fig. 3.4

29. Atomic Packing Factor APF = volume of atoms in unit cell
total volume of unit cell

30. Metallic xl Structures
Face-Centered Cubic (FCC)
Body-Centered Cubic (BCC)
Hexagonal Close-Packed (HCP)

31. FCC f02_03_pg42 Atoms at 8 corners & 6 faces Equivalent of
? whole atoms.
Atomic Packing Factor
(APF)= .74
f02_03_pg42
f02_03_pg42.jpg
Fig. 3.1

32. FCC Cubic structure STM of Platinum
Dept. Kings.edu/chemlab, Property of IBM

33. What’s an STM image?
A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level.

34. You are under our control!
Atoms….
You are under our control!

35. 1990: IBM scientist Don Eigler used an STM to move single xenon atoms on a nickel surface
The engineers moved 35 atoms to spell out "IBM" in a 10 micrometer logo.

36. FCC examples Lab-grown copper (SEM) Etched Aluminum (SEM)
0.3 mm
Lab-grown copper (SEM)
Etched Aluminum (SEM)
Galena (Pb ore)
Gold

37. What’s an SEM image?
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with electrons in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition.
A scanning electron microscope (SEM) produces images by scanning a sample with a focused beam of electrons. Yields topography and composition.

38. BCC f02_03_pg42 Atoms at 8 corners & 1 in center of cube
f02_03_pg42.jpg
Atoms at 8 corners & 1 in center of cube
Equivalent of ? whole atoms
APF = .68
Fig. 3.2

39. BCC Cubic structure STM of Aluminum (100) surface

40. BCC examples
Molybdenum
Iron

41. Metallic xl Structures
Face-Centered Cubic (FCC)
Cu, Al, Ag, Au, Pb, Ni, Pt
Body-Centered Cubic (BCC)
Na, Fe, Cr, Mo, W
Hexagonal Close-Packed (HCP)
Ti, Zn, Cd, Co, Mg

42. f07_03_pg54 Hexagonal System a1 = a2 = a3 ≠ z = 90º g = 120º Fig. 3.7
f07_03_pg54.jpg
Fig. 3.7

43. HCP f03_03_pg43 Atoms at 12 corners, 3 in interior,
2 centered on basal planes
Equivalent of ? whole atoms
(APF)= .74
f03_03_pg43.jpg
Fig. 3.3

44. Hexagonal structure STM of Nickel surface structure.
Dept. Kings.edu/chemlab, Property of IBM

45. Hexagonal structure
Zinc hand sample 45

46. Hexagonal structure SEM of Fine Cadmium powder SEM of ZnO nanowires

47. HCP Examples
Cadmium crystal bar
Titanium crystals
Magnesium (SEM)

48. Atomic Packing Factors
BCC = FCC = HCP = 0.74