4 -1 Introduction to Chem Bonding

1. 4-1 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. 4-2 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 IONIC COVALENT Formula Unit Molecular Formula NaCl CO2

9. *Molecular formula:(struct form) 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. 4.3 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. B. Types of Bonds COVALENT IONIC e- are transferred from metal to nonmetal e- are shared between two nonmetals Bond Formation Type of Structure true molecules crystal lattice Physical State liquid or gas solid Melting Point low high Solubility in Water yes usually not yes (solution or liquid) Electrical Conductivity no Other Properties odorous

24. 4.4 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. B. Types of Bonds METALLIC e- are delocalized among metal atoms Bond Formation Type of Structure “electron sea” Physical State solid Melting Point very high Solubility in Water no yes (any form) Electrical Conductivity malleable, ductile, lustrous Other Properties

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

29. B. Types of Bonds RETURN

30. B. Types of Bonds RETURN

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

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

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

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

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

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

40. C. Bond Polarity Examples: • Cl2 • HCl • NaCl 3.0-3.0=0.0 Nonpolar 3.0-2.1=0.9 Polar 3.0-0.9=2.1 Ionic

41. 4.5 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) • Linear • Tetrahedral • Trigonal pyramidal • Bent