Types of Bonds. Lewis Dot. Lewis Dot. Ionic vs. Molecular Compounds. Lewis Dot. Lewis Dot. Types of Bonds 2/27/2012

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1 Types of Bonds A. Electronegativity The ability of an atom to attract electrons to itself in a bond 1. Periodic Trends (link to size) Metals Low Electronegativity Non Metals High Electroneg The smaller the atom, the higher the electronegativity Ionic vs. Molecular Compounds Ionic Compounds Metal + NonMetal Stealing of Electrons Called Salts Clumps of Ions No prefixes, may need Roman # Molecules Two Nonmetals Sharing of electrons (Covalent or Polar Cov.) Separate Molecules Polar and NonPolar Molecules (H 2 O vs CH 4 ) Prefixes 3. Types of bonds Electroneg. Difference Ionic >2 Polar Cov Covalent <0.2 Example: Li F Types of Bonds Which of the following form predominantly ionic, covalent, or polar covalent bonds? BCl NaF CCl PH PCl OH 1

2 L. Dot for Ionic Compounds Why do Ionics steal? To gain an Octet Draw Pictures for: NaCl CaCl 2 BaO Li 2 O Lattice Energy Energy required to convert a mole of an ionic solid to its gaseous ions NaCl(s) Na + (g) + Cl (g) Increases as distance (d) decreases Increases with increasing charge (Q) U = k Q 1 Q 2 d Melting Point and Charge MgCl 2 MgO (778 o C) (2800 o C) CaCl 2 CaO (772 o C) (2528 o C) Which would have a higher lattice energy? a. NaCl or KCl b.cabr 2 or Ca 3 N 2 c. NaCl or NaBr d.cai 2 or CaO Old School s Molecular Compounds CH 4 CO 2 C 2 H 4 H 2 O HCN C 2 H 2 2

3 Michael Faraday's Benzene Sample (1825) s The Lone Pear(Pair) rides again! Rules 1. Sum all valence electrons, including charges 2. Single Bonds 3. Outer atoms get an octet except H 4. Center gets rest even if it violates the octet 5. Double/triple bonds if center atom still does not have an octet s s NH 3 You try: NCl 3 SF 4 SF 6 H 2 SO 4 CO 2 HCN KrF 4 Cl 2 O ClF 5 NH 2 CH 3 3

4 CH 3 CH 2 CHCH 2 s s CN ICl 4 CHCCH 2 NCl 2 BrO 3 NO + s Resonance Structures You try: CO 3 2 IBr 4 BF 4 SO 2 4 WarmUp: O 3 Definition When a molecule can exist in more than one arrangement of electrons 1. Atoms remain static 2. Only the electrons move Examples Resonance Structures NO 2 CHO 2 HNO 3 Benzene Resonance Structures Which needs resonance, SO 3 or SO 3 2 SO 2 Order the species in the previous problem from shortest to longest bond length. SO 2 2 4

5 Less Than an Octet More Than an Octet Hydrogen Only gets 2 Beryllium, Boron, and Aluminum BeCl 2 BF 3 AlF 3 Just follow the rules and you will be able to draw these Ex: AsF 6 Strengths of Covalent Bonds Single < Double < Triple Bond Strength (kj/mole) Bond Length (Å) CC C=C C = C N = N Calculating Enthalpies of Reaction H rxn = H broken made Let s look at bonds broken and made Calculate the heat of reaction for the following reaction. CH 4 (g) + Cl 2 (g) CH 3 Cl(g) + HCl(g) HCH 3 + ClCl ClCH 3 + HCl Bonds broken: One mol CH, One mol ClCl Bonds made: One mol CCl, One mol HCl 5

6 H rxn = H broken made H rxn = [1(CH) + 1(ClCl)] [1(CCl) + 1(HCl)] H rxn = [413 kj kj] [328 kj kj] H rxn = 104 kj (Exothermic reaction) Calculate the H for the following reaction: Bonds Broken Bonds Made 6 CH 4 C=O 1 CC 6 OH 7/2 O 2 H rxn = H broken made H rxn = [6CH + 1CC + 7 / 2 O 2 ] [4C=O + 6OH] H rxn = [6(413) + 1(348) + 7 / 2 (495)] [4(799) + 6(463)] Calculate the H for the following reaction: H rxn = 1416 kj (Exothermic reaction) 6

7 Bonds Broken Bonds Made 4 NH 1 N=N 1 NN 2 HH H rxn = H broken made H rxn = [4NH + 1 NN] [1 N=N + 2 HH] H rxn = [4(391) + 1(163)] [1(941) + 2(436)] H rxn = 86 kj (Exothermic reaction) Double Bonds Calculate the enthalpy change for the following reaction. Be sure to always break the multiple bond and remake a single CC bond. Br Br HC=CH + Br 2 HCCH H H H H (ANS: 93 kj) Double Bonds Calculate the enthalpy change for the following reaction. If the enthalpy change for the following reaction is 0 kj, calculate the CCl bond energy. H H HC=CH + 2H 2 HCCH H H (ANS: 289 kj) CH 3 Cl(g) + H 2 O(g) CH 3 OH(g) + HCl(g) Bond energy HCl 430 kj/mol C O 360 kj/mol OH 460 kj/mol (ANS: 330 kj/mol) If the enthalpy change for the following reaction is 1995 kj, calculate the bond energy of C=O. Suffix Organic Naming Suffix Class Characteristic ane Alkane All single bonds C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O(g) Bond energy CC 345 kj/mol CH 415 kj/mol O kj/mol OH 460 kj/mol (800 kj) ene Alkene Double bond(s) yne Alkynes Triple bond(s) 7

8 IUPAC Names of Alkanes Suffix = ane Name the following and write the chemical formula # of C atoms Name & Formula # of C atoms Name & Formula 1 Methane CH 4 6 Hexane C 6 H 14 2 Ethane C 2 H 6 7 Heptane C 7 H 16 3 Propane C 3 H 8 8 Octane C 8 H 18 4 Butane C 4 H 10 9 Nonane C 9 H 20 5 Pentane C 5 H Decane C 10 H [Ca] Lewis 2+ 2[F] Dot (8 ve around F) 16. BaF 2 CsCl Li 3 N Al 2 O 3 20 a) KF has a larger LE because F is much smaller than Cl b) Na Cl ~ 2.8 A KF ~ 2.7A 22. a) (i) Increases with charge (ii) decreases with d b) KBr < NaF < MgO < ScN 24 a) Ca 2+ is smaller than Ba 2+, higher LE b) NaCl is smallest pair, highest LE c) BaO has highest charges, highest LE 34. a) Draw LD of H 2 O 2 and O 2 b) O 2 has a double bond, shorter bond length 38. a) O b) Al c) Cl d) F 40. a) OF < CF < BeF b) SBr < CP < OCl c) CS < NO < BF 50.Bond Length SO 2 < SO 3 < SO CO 2 (no resonance needed) 54. Bond Length NO + < NO 2 <NO a) 104 kj b) 20 kj c) 5 kj 68. a) 2023 kj b) 1255 kj c) 192 kj 70. a) 124 kj b) 137 kj 1. a) C 2 H 3 Cl 3 O 2 b) Same 8

9 In 2 S (I) [Kr]5s 2 4d 10 InS (II) [Kr]5s 1 4d 10 In 2 S 3 (III) [Kr]4d 10 In(III) is smallest (least mutual electron repul) In(III) has the highest lattice energy 102.a) C 2 H 3 Cl 3 O 2 b) C 2 H 3 Cl 3 O 2 c) Structure CCl 3 CH(OH) 2 9