VWT 272 Class 4. Quiz 3. Number of quizzes taken Min 7 Max 30 Mean 22.7 Median 28 Mode 30

Transcription

1 VWT 272 Class 4 Quiz 3 Number of quizzes taken Min 7 Max 30 Mean 22.7 Median 28 Mode 30

2 Week 4 The Molecule and Bonding Once we understand how molecules are formed, we can manipulate them. If you can manipulate molecules, you can manipulate genes and matter, you can synthesize new material - the implications are just unbelievable. Ahmed Zewali (1946 -?)

3 Plan of Study Review of the Atom & the Periodic Table The Molecule Ionic Bonds Covalent Bonds Simple Chemical Structures

4 What We Learned About the (Bohr) Atom Atoms are the smallest unit of an element Elements are different due to the mass of their atoms The mass is mostly in the nucleus The nucleus is the home of positive and neutral particles Negatively charged electrons move around the nucleus in fixed orbits Atoms are have no charge so the number of electrons (-) and protons (+) are equal The chemical properties of each element is determined by the number of electrons in the outer orbits of its atoms

5 What We Learned About the (Bohr) Atom

6 The Shell Model of the (Bohr) Atom

7 The Orbital Shells Electrons Outside of the Nucleus Occupy discrete areas/energy levels - shells 4 types of shells (s, p, d, h) Negative charge (-) Light (5.486 x 10-4 u) Responsible for chemical bonding Can move between nuclei to form ions Ion is an atom that has more or fewer electrons than protons

8 The Ion Note that the LOSS of an negatively (-) charged electron makes the resulting ion positive (+) Ions with a positive charge are called cations Ions with a negative charge are called anions

9 You Can t Buy Ions! a cation (+) can t exist without an anion (-)

10 Modern Periodic Table So two months ago!

11 The Periodic Table Horizontal Rows are called Periods Left to Right Mass increases slowly Properties change metals metalloids non-metals Nobel gasses Vertical Columns are called Groups Top to Bottom Mass increases rapidly Properties remain similar Alkali Metals (Li, Na, K, etc.) highly reactive form 1 + ions Alkaline Earth Metals (Be, Mg, Ca, etc.) very reactive form 2 + ions Halogens (F, Cl, Br, etc.) low boiling temperatures form 1 - ions Noble Gasses (He, Ne, Ar, etc.) Very unreactive form NO ions

12 Chemistry is the Search for Nobility

13 Chemistry is the Search for Nobel-ity

14 Chemistry is the Search for Nobel-ity

15 Chemistry is the Search for Nobility

16 Neon (Ne) Noble Gasses

17 Argon (Ar) Noble Gasses

18 The Octet Principle Gilbert Lewis ( ) American In chemical compounds, atoms tend to have the electron configuration of a noble gas. Coined The Rule of 8 There are 8 valence electrons in most atoms in chemical compounds Nominated 35 times for a Nobel Prize

19 The Octet Principal Noble Gasses have a Full outer shell 8 electrons in 4 pairs Except H and He which have an outer shell of 2 electrons Outer electrons called Valence Electrons Lewis Dot Structure of Ne

20 Lewis Dot Structures More Lewis Dot Structures

21 You Can t Buy Ions! a cation (+) can t exist without an anion (-)

22 Opposites Attract Ionic Bonding Na + Cl Na + + Cl - NaCl

23 Opposites Attract Ionic Bonding Na + Cl Na + + Cl - NaCl

24 Opposites Attract Ionic Bonding Is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds. (Wikipedia)

25 Opposites Attract Ionic Bonding Mg + Cl + Cl Mg 2+ + Cl - + Cl - MgClCl Mg + 2Cl Mg Cl - MgCl 2

26 Opposites Attract Ionic Bonding Examples Sodium bromide - NaBr Potassium Chloride KCl Calcium Chloride CaCl 2 Magnesium Oxide MgO Metals to Nonmetals

27 Sharing is Caring Covalent Bonding Cl + Cl ClCl Cl 2

28 Sharing is Caring Covalent Bonding Cl + Cl ClCl Cl 2

29 Sharing is Caring Covalent Bonding Examples Hydrogen Cloride HCl Oxygen Dihydroxide H 2 0 Methane - CH 4 Nonmetals to Nonmetals

30 Sharing is Caring Covalent Bonding Examples H + Cl HCl

31 Sharing is Caring Covalent Bonding Examples 2H + O H 2 O

32 Sharing is Caring Covalent Bonding Examples 4H + C CH 4

33 The Worst Bond Movie Ever!

34 The Cutest Bond Movie Ever!

35 Polar Covalent Bonds Middle ground between Ionic and Covalent Bonds

36 Electronegativity If the difference is between 0.0 and 0.4 non-polar covalent bond If the difference is between 0.4 and 1.7 polar covalent bond If the difference is > 1.7 ionic bond

37 Pauling s Teeter Totter

38 Pauling s Teeter Totter A B If two atoms have equal electronegativity both have the same desire to attract the bonding pair of electrons electrons will be found on average half way between the atoms Covalent Bond

39 Pauling s Teeter Totter A δ+ B δ- If two atoms have slightly different electronegativity one atom (B) will have more desire to attract the bonding pair of electrons electrons will be found on average closer to the more electronegative atom Polar Covalent Bond

40 Pauling s Teeter Totter A + B - If two atoms have highly different electronegativity one atom (B) will have a lot more desire to attract the bonding pair of electrons electrons will be found on average very close to the more electronegative atom Ionic Bond

41 Electronegativity Increases Across a Period If the difference is between 0.0 and 0.4 non-polar covalent bond If the difference is between 0.4 and 1.7 polar covalent bond If the difference is > 1.7 ionic bond

42 Patterns of Electronegativity Factors that explain electronegativity The number of protons in the nucleus More positively charged protons Na vs. Cl» Na has 11 protons» Cl has 17 protons

43 Electronegativity more protons - more better 11Na + 17Cl -

44 Electronegativity Decreases Down a Group If the difference is between 0.0 and 0.4 non-polar covalent bond If the difference is between 0.4 and 1.7 polar covalent bond If the difference is > 1.7 ionic bond

45 Patterns of Electronegativity Factors that explain electronegativity The shielding by the electrons in closer shells More negatively charged electrons in the way F vs. Cl» F has 9 protons shielded by 2 electrons» Cl has 17 protons shielded by 10 electrons

46 Electronegativity more electrons - more shielding H + Cl - H + H + F -

47 Polar Bonds and Polar Molecules Bar Magnet One end (pole) is attractive to positive charges Other end (pole) is attractive to negative charges δ+ δ-

48 Polar Bonds and Polar Molecules J.J. Thompson - Movie Star!

49 The Atom & Dead White Men Joseph John Thomson ( ) England Discovered the first sub-atomic particle, the Corpuscles (Electron) About 1,840 times lighter than Hydrogen Always the same Negatively charged Won the Nobel Prize 1906

50 Polar Bonds and Polar Molecules J.J. Thompson - Movie Star!

51 Polar Bonds and Polar Molecules Cl 2 Cl has an electronegativity of 3.0 Cl has an electronegativity of 3.0 So bond is Non-Polar Covalent Electrons and charge are equally distributed around the molecule Molecule is Nonpolar

52 Polar Bonds and Polar Molecules Carbon Tetrachloride CCl 4 Cl has an electronegativity of 3.0 C has an electronegativity of 2.5 So bonds are Polar Covalent Partial charge is equally distributed around the molecule Molecule is Nonpolar

53 Polar Bonds and Polar Molecules Chloroform CHCl 3 Cl has an electronegativity of 3.0 C has an electronegativity of 2.5 H has an electronegativity of 2.1 So all bonds are Polar Covalent Partial charge is NOT equally distributed around the molecule Molecule is Polar

54 Polar Bonds and Polar Molecules Carbon Tetrachloride vs. Chloroform δ+ δ-

55 Water a Polar Covalent Molecule

56 Drawing a Single Bond H 2

57 Bond, Single Bonds Ethanol Octane

58 Sharing is Caring x2 & x3 Double and Triple Bonds

59 CO 2 One Carbon Carbon Dioxide 4 valence electrons Two Oxygen 6 valence electrons Total valence electrons 4 + (6 x 2) = 16

60 HCN One Carbon 4 valence electrons One Hydrogen 1 valence electron Ḣ One Nitrogen 5 valence electrons Total valence electrons = 10 Hydrogen Cyanide

61 Bond Length Compound Simple Formula Name Bond Order Bond Length (pm) Bond Dissociation Energy (kj/mol) H 3 C CH 3 C 2 H 6 Ethane H 2 C=CH 2 C 2 H 4 Ethylene HC CH C 2 H 2 Acetylene

62 Methanol - 6 Ways

63 Our New BFF, Carbon

64 Propane - 4 Ways

65 Bond, Single Bonds The Sequel Ethanol Octane

66 Some Molecules in Wine Ethanol (C 2 H 6 O or C 2 H 5 OH ) Glucose (C 6 H 12 O 6 )

67 Next Week More Chemical Nomenclature Introduction to Acids and Bases ph and TA