2. 1 Wednesday!!!!! 3/28/12 Bell Ringer 1)Pick up the practice sheet off the front demo table and complete it. 2)Get out your notes from yesterday Schedule 1.Bell Ringer 2.Periodic Trends Practice 3.Go over Tests 4.Bonding Notes PAP Chemistry You gain strength, courage, and confidence by every experience in which you really stop to look fear in the face. You must do the thing which you think you cannot do. I CAN……solve chemistry problems by being an independent, creative thinker.

3. 2 Alkali Metals Alkaline Earth Metals Transition Metals Halogens Noble Gases

4. 3 Atomic Radius –size of atom © 1998 LOGAL zFirst Ionization Energy Energy required to remove one e - from a neutral atom. © 1998 LOGAL zMelting/Boiling Point

5. 4 Atomic Radius Increases as you move DOWN a family Decreases as you move ACROSS a period. Atomic Radius

6. 5 Why larger going down? –Higher energy levels have larger orbitals –Shielding - core e - block the attraction between the nucleus (positive protons) and the valence (negative) e - Why smaller to the right? –Increased nuclear charge without additional shielding pulls e - in tighter (adding electrons and protons, but not adding energy levels) Atomic Radius

7. 6 First Ionization Energy Increases ACROSS a period Decreases DOWN a group/family Ionization Energy

8. 7 Why opposite of atomic radius? –In small atoms, e - are close to the nucleus where the attraction is stronger Why small jumps within each group? –Stable e - configurations don’t want to lose e - Ionization Energy

9. 8 Melting/Boiling Point Highest in the middle of a period. F. Melting/Boiling Point

10. 9 Ionic Radius Cations (+) xlose e - xsmaller © 2002 Prentice-Hall, Inc. Anions (–) xgain e - xlarger Ionic Radius

11. 10 Measure of the ability of an atom in a chemical compound to attract electrons Increases ACROSS a period Decreases DOWN a group/family Electronegativity

12. 11 Which atom has the larger atomic radius? Be orBa Ca orBr Ba Ca Examples

13. 12 Which atom has the higher 1st I.E.? NorBi Ba orNe N Ne Examples

14. 13 Which atom has the higher melting/boiling point? LiorC CrorKr C Cr Examples

15. 14 Which particle has the larger ionic radius? SorS 2- AlorAl 3+ S 2- Al Examples

16. 15 Which element has the higher electronegativity? SorF AlorIn F Al Examples

17. 16 Friday!!!!! 3/30/12 Bell Ringer 1)Get out your notes from yesterday & answer the following question: 1)Draw the Lewis Dot Notation for the following elements: Na Cl B C N O Schedule 1.Bell Ringer 2.Go over Tests 3.Bonding Notes PAP Chemistry You gain strength, courage, and confidence by every experience in which you really stop to look fear in the face. You must do the thing which you think you cannot do. I CAN……solve chemistry problems by being an independent, creative thinker.

18. 17 Chemical Bonding and Molecular Structure Chemical Bonding and Molecular Structure Cartoon courtesy of NearingZero.net

19. 18 Bonding Chemical Bond –attractive force between atoms or ions that binds them together as a unit –bonds form in order to… »decrease chemical potential energy (PE) »increase stability

20. 19 Intra VS Intermolecular Forces INTRA  within INTER  between, among 1. Intramolecular force: bonds between atoms or ions in molecules Examples: metallic, covalent, & ionic bonds –Hydrogen bonds to oxygen and forms water 2. Intermolecular force: attraction between molecules themselves Intermolecular forces are only associated with covalently bonded molecules (glucose & fructose hydrogen bridge to make sucrose) –3 different levels of strength: » a) Hydrogen Bridge (used to be called H bond) (strongest) »b) Dipole-dipole forces » c) London Dispersion forces (weakest) (covalently bonded molecules have this) –Water molecule attracted to another water molecule

21. 20 Review of Chemical Bonds There are 2 main types of bonding:There are 2 main types of bonding: IONIC—transfer of 1 or more valence electronsIONIC—transfer of 1 or more valence electrons COVALENT—sharing of valence electronsCOVALENT—sharing of valence electrons “Between ionic and covalent most bonds are”

22. 21 The type of bond can usually be calculated by finding the difference in electronegativity of the two atoms that are going together.

23. 22 Electronegativity Difference If the difference in electronegativities is between: – 1.7 to 4.0: Ionic – 0.3 to 1.7: Polar Covalent – 0.0 to 0.3: Non-Polar Covalent Example: NaCl Na = 0.8, Cl = 3.0 Difference is 2.2, so this is an ionic bond!

24. 23 Ionic Bonds Ions are positively or negatively charged atoms due to the removal or addition of an ELECTRON 1.CATION (CAT – ION) is positively charged – electron removed. 2.ANION (AN – ION) is negatively charged – electron gained. In general metals (Mg) lose electrons ---> cations (+) nonmetals (F) gain electrons ---> anions (-)

25. 24 Ionic Bonds Positive cations and the negative anions are attracted to one another (remember: Opposites Attract!) Therefore, ionic compounds are usually between metals and nonmetals (opposite ends of the periodic table).

26. 25 Comparison Ionic Compounds Crystalline solids (made of ions) High melting and boiling points Conduct electricity when melted Many soluble in water but not in nonpolar liquid Metal and nonmetals bond Covalent Compounds Gases, liquids, or solids (made of molecules) Low melting and boiling points Poor electrical conductors in all phases Many soluble in nonpolar liquids but not in water Nonmetals bond with other nonmetals

27. 26 Diagram Ionic Bonding NaCl K & S Al & Cl Al & O

28. 27 Get out the practice problems from Friday and your notes on Bonding Paired Excercises: 1,5,7,9,11,13,15,23,25, Happy April 2 nd !!

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46. 45 A chemical bond in which two or more electrons are shared by two atoms. How should two atoms share electrons? F F + 7e - FF 8e - F F F F Lewis structure of F 2 lone pairs single covalent bond Covalent Bond

47. 46 8e - H H O ++ O HH O HHor 2e - Lewis structure of water Double bond – two atoms share two pairs of electrons single covalent bonds O C O or O C O 8e - double bonds Triple bond – two atoms share three pairs of electrons N N 8e - N N triple bond or

48. 47 Double and even triple bonds are commonly observed for C, N, P, O, and S H 2 CO SO 3 C2F4C2F4C2F4C2F4

49. 48 Wednesday 4/18/12 1. Draw the Lewis dot structure for HCl. 2. If the penguin represents a hydrogen atom and the polar bear represents a chlorine atom, what does the ice cream represent in the drawing? What do you think the picture is trying to illustrate? 3. Do you think HCl will be attracted to a charged wand? Explain your thinking. 1. Get out your lab from yesterday and turn it in to your tray. Get out paper for notes.

50. 49 Intraparticle vs. Intermolecular Force INTRAPARTICLE ATTRACTIONS (Types of Bonding WITHIN a substance; atom to atom bonding) INTERMOLECULAR FORCES (Types of forces BETWEEN neighboring molecules; molecule to molecule) IonicNA MetallicNA CovalentDipole-Dipole H-bridges London Dispersion Forces (LDF)

51. 50 Thursday 4/19/12 Get out your notes from yesterday. Draw the Lewis structure of the following molecules and identify if they are ionic, polar covalent, or nonpolar covalent: –1. NaCl –2. NO 2 - –3. CH 4

52. 51 Polarity A molecule, such as HF, that has a center of positive charge and a center of negative charge is said to be polar, or to have a dipole moment. A molecule, such as HF, that has a center of positive charge and a center of negative charge is said to be polar, or to have a dipole moment.

53. 52 Dipole Moment Direction of the polar bond in a molecule. Arrow points toward the more electronegative atom. H Cl ++ -- Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

54. 53 H F F H Electrons are shared unequally A covalent bond with greater electron density around one of the two atoms resulting in partial charges (dipole) electron rich region electron poor region e - riche - poor ++ -- Polar Covalent Bond

55. 54 Bond Polarity HCl is POLAR because it has a positive end and a negative end. (difference in electronegativity) Cl has a greater share in bonding electrons than does H. Cl has slight negative charge (-  ) and H has slight positive charge (+  )

56. 55 This is why oil and water will not mix! Oil is nonpolar, and water is polar.This is why oil and water will not mix! Oil is nonpolar, and water is polar. The two will repel each other, and so you can not dissolve one in the otherThe two will repel each other, and so you can not dissolve one in the other Bond Polarity

57. 56 Bond Polarity “Like Dissolves Like”“Like Dissolves Like” –Polar dissolves Polar –Nonpolar dissolves Nonpolar

58. 57 Determining Molecular Polarity Nonpolar Molecules -Electrons are shared equally -Symmetrical electron density -Often identical atoms -Dipole moments are symmetrical and cancel out. BF 3 F F F

59. 58.. Polar Bonds H Cl Polar A molecule has a zero dipole moment because their dipoles cancel one another. HH O Polar FF B F Nonpolar H H H N Polar Nonpolar FF Cl F F F Xe FF Cl C NonpolarPolar Cl H C H H

60. 59 Hydrogen Bridge Occurs with polar covalent structures only Includes a positive Hydrogen ion bonding directly to a negative ion DNA, RNA, and enzymes have many Hydrogen bonding sites Strongest intermolecular force

61. 60 London Dispersion forces Also known as van der Waals bonds Occur only with nonpolar structures Weakest intermolecular force Electrostatic bonds between atoms or molecules Temporary dipole moment

62. 61 MOLECULAR GEOMETRY

63. 62 VSEPR VSEPR V alence S hell E lectron P air R epulsion theory.V alence S hell E lectron P air R epulsion theory. Most important factor in determining geometry is relative repulsion between electron pairs.Most important factor in determining geometry is relative repulsion between electron pairs. Molecule adopts the shape that minimizes the electron pair repulsions. MOLECULAR GEOMETRY

64. 63 Some Common Geometries Linear Trigonal Planar Tetrahedral

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66. 65 Other VSEPR charts

67. 66 Structure Determination by VSEPR Water, H 2 O The electron pair geometry is TETRAHEDRAL The molecular geometry is BENT. 2 bond pairs 2 lone pairs

68. 67 Structure Determination by VSEPR Ammonia, NH 3 The electron pair geometry is tetrahedral. The MOLECULAR GEOMETRY — the positions of the atoms — is TRIGONAL PYRAMID.