Ch. 7 and 8 Bonding

1. Ch. 7 and 8 Bonding Valence Electrons = electrons found in the last occupied shell of an atom (their “changeable” electrons in their last shell) KC3 = It is the same as the “A” group number

2. Lewis Dot Structures = shorthand representations of the chemical symbol and the valence electrons lose 1 lose 2 lose 3 gain 4 gain 3 gain 2 gain 1 no change lose 4 +1 +2 +3 +- 4 -3 -2 -1 0

3. KC 4 = Metals tend to lose electrons and non-metals tend to gainKC 5 = Losing electrons, usually a metalNa  Na+ + e-Pseudo Noble Gas = when an atom gains or loses electrons until they have a full/stable octet (8). They “behave” like a noble gas.

4. KC 6 = Anions form by gaining electrons, usually a non-metal Cl + e-  Cl- Halide ion = at atom from the halogen group that has gained an electron and become an anion (negative ion)

5. Section 7.2 Ionic Compound - a compound formed from the bonding of a cation and an anion KC 14 = Electrically neutral, the positive cation and the negative anion cancel each other out Ionic Bond - the electrostatic bond that holds ions together (the “magnetic” attraction that pulls + and - together)

6. Chemical Formula - shows the kinds and numbers of atoms in the smallest representative unit of that substance

7. Formula Unit - one “functional piece” of that substance in lowest whole number ratio

8. Magnesium and Chlorine? F? Ca and Cl?

9. Aluminum and Bromine? Na and O? Na and N? Ca and O? Ca and N? Al and S? Al and N? The atoms react to cancel out their charges.

10. Ionic Properties Metal and a Nonmetal Neutral Charge Strong Intermolecular Attraction Solid Crystalline Lattice High Melting/Boiling Points Liquid form conducts Electricity

11. Coordination Numbers Cesium Chloride Formula Unit - the lowest ratio of atoms in an ionic compound = “one piece”

12. Jump to Chapter 8Skip Ch. 7.3

13. Covalent Bonding Ch. 8 Covalent Bond = An equal SHARING of valence electrons usually between two or more nonmetals. (A tug of war between two elements trying to gain electrons) Molecule = a particle joined together by covalent bonds and has no net charge Molecular compound - composed of molecules Diatomic - two atoms covalently bonded

16. Molecule vs. Formula Unit A molecule can exist as a single entity (one piece of a gas). An ionic compound cannot they are called “network” solids. Therefore it isn’t an individual molecule its called a formula unit KC 1 = Molecular Compounds or Covalent Bonds usually have low melting and boiling points (already gases and liquids)

17. Compare and Contrast Ionic and Covalent/Molecular Properties

18. Skip to Ch. 8.4 Nonpolar Covalent - electrons shared equally Polar Covalent - electrons shared, but unequally KC 32 = The more electronegative (greedy)atom attracts electrons more strongly and therefore gains a slight negative charge, the less electronegative atom gains a slight positive charge

21. Use the chart to the right to calculate the difference beteween the electronegativity values and determine the bond type. F = 4.0 Li = 1.0 4.0 - 1.0 = 3.0 Ionic

24. Ionic vs Polar vs Covalent Covalent (O2 gas) Polar (H2O) Ionic (NaCl) Share electrons equally Unequal Exchange Gas/Liquid Liquid Solid Low MP and BP Moderate High MP + BP No conducting Electricity Poor Good Conductor

25. Polar Carbon + Hydrogen Unequal share Moderate MP and BP Liquids and Gases Moderate Bonds Poor Conductivity Poor to moderate Some overlap

26. Go back to Ch. 7.3 Metallic Bonding KC23 = As a “sea” of mobile valence electrons each metal atom wants to lose, so therefore they just pass the electrons around between atoms

27. Metallic Bond = The attraction of the free-floating valence electrons for the positively charged metal ions Mobile electrons result in metals that are shiny and good conductors of heat and electricity, and the lack of permanent/consistent bonds means they are malleable and ductile Contrasted with Ionic bonds which are not malleable because the bonds are more permanent, and therefore not malleable, likely to break when struck

28. KC 24 = very compact and orderly, similar to a ionic crystals

30. Alloy = a homogenous mixture of 2 or more metals KC 25 = the properties of alloys are often superior to the component elements Sterling silver (Ag and Cu) Cast Iron (Fe C) Brass (Cu Zn) Bronze (Cu Sn)

31. Stone Age = Flint tools and weapons, Gold discovered, but too soft, not a good tool/weapon Copper Age = decent tool/weapon (3800BC Melting Ores, Cu melting temp relatively low 1083C) Bronze Age = 2800BC natural alloys of copper and tin, unbelievably useful, weapons and tools, but mostly for ruling class and armies, powerful civilizations Iron Age - 1500BC Iron abundant but relatively high melting point (1500C) makes hard to work with in primitive forge, literally hammer out impurities, and reforge (but still not better than Bronze) Steel Age - 1100BC heating iron in a forge with Charcoal (carbon) then water quenching = Steel China is melting and casting Iron by 500BC, and this isn’t done in Europe until 1100AD. Wow!!

32. Electrochemical cell = a device capable of either deriving electrical energy from chemical reactions, or facilitating chemical reactions through the introduction of electrical energy. A battery is an electrochemical cell. It separates two types of metal immersed within a strong ionic solution (electrolyte). The property for the tendency of metals to exchange electrons is enhanced when immersed in a strong ionic solution, that allows the electrons to flow between the two different metals. This flow of charge is electricity.

34. The property for the tendency of metals to exchange electrons is enhanced when immersed in a strong ionic solution, that allows the electrons to flow between the two different metals. This flow of charge is electricity

35. KC 2 = The number and kinds of atoms in a molecule It doesn’t tell you the STRUCTURE.

36. Structural Formulas Shows you the specific arrangement of the atoms found in a substance C6H12O6 C6H12O6 Isomers - same numbers and kinds of atoms but different structures

37. Models KC 13 = the configuration of noble gases Covalent bonds usually contain the “greedy non-metals

38. Single Covalent Bond two atoms held together by a sharing of a pair of electrons KC 14 shared pairs are dotted in between Or shown as a dashed line in a Formula Unshared pairs - pairs of electrons that are not shared between two atoms

39. Double Bond = a bond from two shared pairs (4 electrons) Triple Bond = A bond from three shared pairs (6 electrons)

40. What is a coordinate covalent bond? One atoms contributes both shared electrons (its less greedy than the one it is bonding to) Give an example of a coordinate covalent bond. Carbon Monoxide KC 16 How is a coordinate covalent bond different from other covalent bonds? The shared pair of electrons comes from one atom, not one from each What is a polyatomic ion? A tightly bound group of atoms that has a charge, and yet behaves as a unit (package)

41. What is bond dissociation energy? Energy required to break a covalent bond between two atoms (Ex: H2 molecule = 435kJ/mol) KC 17 How is the strength of a covalent bond related to its bond dissociation energy? A large bond dissociation energy corresponds to a strong covalent bond. Explain this idea in terms of carbon compounds, like methane and coal, and their relative stability. Carbon and Hydrogen are equally strong in their pull, and therefore hard to separate = stable

42. Bond Dissociation Energies

43. KC 18 Draw the electron dot structure resonance structures of ozone and explain how they describe its bonding. • Ozone is a hybrid, or mixture of the extremes of the resonance forms • What are resonance structures? • A structure that occurs when it is possible to draw two or more valid electron dot structures • KC 19 List three ways in which the octet rule can sometimes fail to be obeyed. • Cannot be satisfied in molecules whose total number of valence electrons is an odd number, there are also molecules in which an atoms has fewer, or more, than a complete octet (like NO2 page 228) • Draw the electron dot structure for sulfur hexafluoride. What is the unique application of sulfur hexafluoride. • Page 229

44. Sigma Bond = two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting the 2 nuclei Pi Bond = the bonding electrons are found in sausage shaped regions above and below the bond axis

46. What is VSEPR theory? • Valence Shell Electron Pair Repulsion Theory • KC 24 Explain how the VSEPR Theory can be sued to predict he shapes of molecules. • Repulsion between electron pairs causes molecular shapes to adjust so the valence-electron pairs stay as far apart as possible

47. 3 4 5 6 7 Each bond counts as an area that shapes the molecule. So does each set of unpaired electrons.

50. KC 34 Compare the strengths of intermolecular attractions to the strengths of ionic bonds and covalent bonds. • Weaker than ionic or covalent bonds • What are van der Waals forces? • Two weakest molecular attractions caused by dipole interactions and dispersions • What are dipole interactions? • Polar molecules attracted to one another • What are dispersion forces? • The weakest force caused by the motion of electrons in a non-polar molecule from one side of the molecule to the other creating temporary dipole charges