Chapter 10 notes

Chapter 10 notes - Chapter 10: Shapes of Molecules Lecture...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Slide No. 1 Chapter 10: Shapes of Molecules ± What's The Point ? ² We learn how atomic orbitals combine to give molecules their observed structure. ± Lewis Dot Structures ² Drawing Lewis Dot Structures of Molecular Compounds ² Resonance ² Formal Charge ± Estimating Bond Enthalpies from Bond Energies ± VSEPR ± Molecule Polarity ± Reading: Entire Chapter ± Homework Problems: 5(6), 9(10a),11(12a), 13(14a), 15(16b), 17(18), 19(20a,b), 21(22b), 26(24), 30(31), 43(44), 45(46), 49(50a,b,d), 51(52), 64(65) Lecture Outline Slide No. 2 10.1 Lewis Dot Structures of Molecules ± Gilbert N. Lewis, American chemist (1875-1946) ± Lewis Structures ² Predict atom connectivity and bond order in molecules ² Predict three-dimensional molecular structure 1) Determine total number of VEs in each atom (ns and np orbitals only). ² Add electrons for anions, subtract for cations. 2) Draw a molecular structure with single bonds between atoms ² H is always terminal (it can only form 1 bond) ² Least electronegative atom is usually the central atom and is often the first atom in the chemical formula (SO 2 , ClO 4 ) ² Each single bond that you drew uses up 2 (shared) electrons 3) Determine # of remaining VEs (subtract 2 x bonds from total) 4) Fill in the octets around the terminal atoms (except H) and again calculate the number of VEs remaining 5) Place remaining electrons around central atom Lewis in 1923 Guidelines for Lewis Diagrams
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Slide No. 3 Guidelines for Lewis Diagrams, Continued 6) 5 possible scenarios at this point: ± All atoms (except H) have 8 electrons around them. (Each bond should be counted as 2 e -. ) Done! ± Central atom has > 8 electrons: OK for Period 3, 4, 5, 6, or 7 atoms. Done! ± Central atom has < 8 electrons: OK for Be (4e), B (6e), or Al (6e). Done! ± Central atom has < 8 electrons and is not Be, B, or Al: form multiple bonds double bond: use one terminal atom lone pair to form the second bond triple bond: use two terminal atom lone pairs from the same atom to form the second bond and third bond. ± Total VE number is odd. Proceed until all atoms have 8e, except for one atom with 7e. 7) For substances with >1 possible resonance structure or substances that can exceed the octet rule (central atoms from period 3 or higher), use formal charge to determine the best resonance structure(s). ± formal charges should be as small as possible ± negative formal charges should be on the most electronegative atoms; positive formal charges on the least electronegative atoms. 10.1 Lewis Dot Structures of Molecules Slide No. 4 Examples of Lewis Diagrams CCl 4 SF 4 BH 3 NO 3 NO 2 Step (1) – Count the Valence Electrons (VEs) 10.1 Lewis Dot Structures of Molecules
Background image of page 2
Slide No. 5 CCl 4 SF 4 BH 3 Step (2) – Draw molecular structure with single bonds: H is always terminal and the least electronegative atom is the central atom.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 17

Chapter 10 notes - Chapter 10: Shapes of Molecules Lecture...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online