1. 6-1 Introduction to Chem Bonding *a link between atoms that results from the mutual attraction of their nuclei for e-

2. -Types of chem bonds 1. Ionic bond: transfer of e- 2. Covalent bond: sharing of e-’s -bonds between unlike atoms are never completely ionic and rarely completely covalent.(Pauling) 3. Metallic bonds: between metals

3. *nonpolar-covalent bond: cov bond which the bonding e-’s are shared equally by the bonded atoms -resulting in a balanced distribution of elect charge

4. *Polar: meaning that they have an uneven distribution of charge *Polar-cov bond: the united atoms have an unequal attraction for the shared e-’s

5. -Why chem bonding occurs -if their PE is lowered by the change, two atoms will form a chem bond.

6. 6-2 Covalent Bonding and Molecular Compounds *Molecule: smallest unit quantity of matter which can exist by itself and retains all the prop of the original substances *Diatomic molecule: 2 like atom

7. *Molecular cmpnd: chem cmpnd whose simplest units are molecules *Chem formula: represents the #’s of atoms of each kind in a chem cmpnd by using atomic symbols and numerical subscripts

8. A. Vocabulary CHEMICAL FORMULA Molecular Formula Unit IONICCOVALENT CO 2 NaCl

9. *Molecular formula: shows types and numbers of atoms combined in a single molecule

10. -Formation of covalent bond *Bond length: aver dist between 2 bonded atoms *Bond nrg: nrg required to break a chem bond and form neutral atoms

11. -The Octet Rule *Octet rule: 8 e-’s in the highest nrg level

12. -Lewis Structure (Gilbert Lewis) *pg 169

13. -Lewis Structure *Unshared pair: pair of e-’s that is not involved in bonding *single bond: cov bond produced by sharing of 1 pair of e-’s between 2 atoms

14. *structural formula: indicates kind, number, arrangement, and bonds of the atoms in a molecule.

15. -Multiple Covalent Bonds *Double bond: cov bond between 2 atoms produce by sharing 2 pairs of e- EX

16. -Multiple Covalent Bonds *Triple bond: cov bond between 2 atoms produced by sharing 3 pairs of e- Ex -Sample problem 6.3

17. -Polyatomic Ions *charged group of cov bonded atoms Ex

18. 6.3 Ionic Bonding and Ionic Compounds *Ionic compound: composed of + and – ions combined so that the + and – charges are equal

19. 6.3 Ionic Bonding and Ionic Compounds *Formula unit: simplest collection of atoms from which a cmpnds formula can be estab -Common ions: Na+, K+, Mg+2, Ca+2, Ba+2, O-2, S-2, F-,Cl-, Br-,I-

20. -Formation of Ionic Bonds *Lattice nrg: nrg released when one mole of an ionic crystalline cmpnd is formed from gaseous ions

21. -Ionic vs Covalent bonds -ionic bonds are stronger than cov bonds -cov bonds ~lower mp, bp, and hardness

22. -Ionic vs Covalent bonds -ionic bonds ~hard and brittle ~carry a current when dissolved in water

23. IONIC COVALENT Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties e - are transferred from metal to nonmetal high yes (solution or liquid) yes e - are shared between two nonmetals low no usually not Melting Point crystal lattice true molecules B. Types of Bonds Physical State solid liquid or gas odorous

24. 6.4 Metallic Bonding -metals have a low ionization nrg and low electroneg. -two metals form at best a weak covalent bond

25. 6.4 Metallic Bonding -metals tend to form what we call a sea of electrons

26. 6.4 Metallic Bonding *Metallic bond: chem bond resulting from the attraction between + ions and surrounding mobile electrons -to compare strengths in metals vaporization heats are used

27. “electron sea” METALLIC Bond Formation Type of Structure Solubility in Water Electrical Conductivity Other Properties Melting Point B. Types of Bonds Physical State e - are delocalized among metal atoms very high yes (any form) no malleable, ductile, lustrous solid

28. -Nature of Metals -the motion of the e- sea helps explain why metals have certain properties *Malleability *Ductility -luster

29. RETURN B. Types of Bonds

30. RETURN B. Types of Bonds

31. Ionic Bonding - Crystal Lattice RETURN B. Types of Bonds

32. Covalent Bonding - True Molecules RETURN B. Types of Bonds Diatomic Molecule

33. Metallic Bonding - “ Electron Sea ” RETURN B. Types of Bonds

34. C. Bond Polarity Most bonds are a blend of ionic and covalent characteristics. Difference in electronegativity determines bond type.

35. C. Bond Polarity Electronegativity Attraction an atom has for a shared pair of electrons. higher e - neg atom   - lower e - neg atom   +

36. C. Bond Polarity Electronegativity Trend (p. 151) Increases up and to the right.

37. Nonpolar Covalent Bond e - are shared equally symmetrical e - density usually identical atoms C. Bond Polarity

38. ++ -- Polar Covalent Bond e - are shared unequally asymmetrical e - density results in partial charges (dipole)

39. Nonpolar Polar Ionic View Bonding Animations.Bonding Animations C. Bond Polarity

40. Examples: Cl 2 HCl NaCl 3.0-3.0=0.0 Nonpolar 3.0-2.1=0.9 Polar 3.0-0.9=2.1 Ionic

41. 6.5 The properties of molecular compounds

42. -VSEPR Theory *electrostatic repulsion between valence e- pairs surrounding an atom causes these pairs to be oriented as far apart as possible

43. (table 6-5 pg 186) 1. Linear 2. Tetrahedral 3. Trigonal pyramidal 4. Bent

44. -Hybridization(fig.6-23 p188) *mixing of two or more atomic orbitals of similar nrg’s on the same atom to give new orbital of equal nrg’s

45. -Hybridization ex: CH 4 -hybridization of s and p yield 4 new identical orbits *hybrid orbitals: orb of = nrg produced by the combination of 2 or more orb on the same atom

46. -Intermolecular Forces *force of attraction between molecules -generally weaker than the bonds that join atoms in molecules, ions in ionic cmpnds, or metal atoms in solid metals

47. ~dipole-dipole forces and molecular polarity -strongest intermol forces act between polar molecules *dipole: = but opp charges separated by a short distance. - arrow points toward the neg pole

48. *DD force: forces of attraction between polar molecules ex: polar vs nonpolar

49. ~hydrogen bonding *an intermolecular attraction between a H atom and an unshared pair of e-’s on a strongly electroneg. Atom

50. ~hydrogen bonding -H bond represented by dotted lines connecting the H to the unshared e- pair of the electroneg atom

51. ~london dispersion forces (Fritz London 1930) *attraction resulting from the constant motion of e-’s and the certain instantaneous dipoles and induced dipoles

52. ~london dispersion forces -between all atoms and molecules -only intermolecular forces acting among noble-gas atoms and nonpolar molecules -LF increases with increasing mass of atoms and molecules