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lecnotes13 - MIT OpenCourseWare http:/ocw.mit.edu 5.111...

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MIT OpenCourseWare http://ocw.mit.edu 5.111 Principles of Chemical Science Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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_______________________________________________________________________________ ________________________________________________________________________________ 5.111 Lecture Summary #13 Readings for today: Section 3.1 ( 3 rd or 4 th ed ) – The Basic VSEPR Model, Section 3.2 ( 3 rd or 4 th ed ) – Molecules with Lone Pairs on the Central Atom. Read for Lecture #14: Section 3.8 (3.9 in 3 rd ed ) – The Limitations of Lewis’s Theory, Section 3.9 (3.10 in 3 rd ed ) – Molecular Orbitals, Section 3.10 (3.11 in 3 rd ed ) – The Electron Configuration of Diatomic Molecules, Section 3.11 (3.12 in 3 rd ed ) – Bonding in Heteronuclear Diatomic Molecules. Topics: I. Polar covalent bonds and polar molecules (continued from Lecture #12) II. The shapes of molecules: VSEPR theory A. Molecules without lone pairs B. Molecules with lone pairs I. POLAR COVALENT BONDS/POLAR MOLECULES (continued from Lect. #12) A polar covalent bond is an unequal sharing of e - s between two atoms with different electronegativities ( χ ). In general, a bond between two atoms with an χ difference of > _____ and < _____ (on the Pauling scale) is considered polar covalent. Polar molecules have a non-zero net dipole moment. In large organic molecules and in biomolecules, such as proteins, we often consider the number of polar groups within the molecule. 1 For example, let’s compare vitamin A to vitamin B9 Which vitamin contains a higher number of polar bonds? vitamin ________ Vitamin A Vitamin B9 (_____________________) ________________ soluble ________________ soluble H 2 C H 2 C C H 2 C C H C C H C H H C C H C C H H 2 C O H
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lecnotes13 - MIT OpenCourseWare http:/ocw.mit.edu 5.111...

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