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Chem+P+Polarity+and+VSEPR-2

Chem+P+Polarity+and+VSEPR-2 - 5 E E s Polarity and Dipole...

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Unformatted text preview: 5' E: E. s Polarity and Dipole Moments Chem P Lecture Handout Series 1 #1 mummivw ‘ugms *M 3* '1 3* {9349.145 first: 3 4 a 4 r a £13} i“; 551 £13! (17') (53} When two unlike atoms are covalently bonded, the shared electrons will be more strongly attracted to the atom of greater electronegativlty. l Quick Quiz #1 E This is a representation of the electron densities in hydrogen fiuoflde. l. l Which atom is hydrogen? On Hm {€93 ] if‘flflf Explain. @3me MSLLfé . has (1. outwit or” separmkm of? Chagfi (choraclelrx'teci lea (upgrades: extremes l: 3 «- “HMS week? I Definition of polar: L; oLl‘gsolvE‘S m wool-elf” (explode lmfir {”8an Apolar bond is: cbmtgnr loam be} m two ahmg m mix/{<1}. er WCWWS We. shwfli UHEQQQHMW Molecules containing polar bonds can exhibit molecular polarity. 3’10“?” CL“ mobCUQS with Polar bmdls are +Mmaeloes polar“ Polarity and Dipole Moments Chem P Lecture Handout Series #2 How does moiecuiar geometry (shape) affect molecular dipoles? Exampie: Carbon Dioxide Why is C02 a nonpolar molecule? Lewis Dot Structure Or; C :3" O TLL CFO PQ’L'VS home r'jUt/LCQI awmagcmmie to”? bm&"‘“§ MOE With Partial Charges honbmah‘mé chLEh/ms . So i even. J: Ufl-I— 6: though each C» C) 'meE is PGEM'} O h: C 2 O Pb. lle/‘Svi‘C/{MOQE oE/LPOELQ Vtflm‘f‘é Came-3i moi fit me EQWLQ “*5 With Bond Dipioes a: whoh’ifi‘ nonpoim/ gap“? 1 “3‘ . t d .t.\ O:C:O (no ne‘E‘ cit/cook mommy} E i . " 0V6; i E Shape =r- fitmeocx’“ FEW BMW E Draw each of the above structures for water. Lewis D015 Structure But there is an important piece of information missing? H # E?” H SENCLPE, How have you seen water drawn or With Partial Charges a”? d: {\r depicted in a textbook? H—OPH . _ O = Wlth Bond Diploes / \ W Hamfl? Hwos Ks, NOELCUEOLV (Mimic is 0. Huh? H H i '31 ”Erhaug’bl' wairev wotfi polar". Partial Charges - the bonding electrons are shared in each compound, but are not always shared equally. - electrons spend more of the time closer to most electronegative element. As a result, that atom acquires a "partial" negative charge. At the same time, the lesser electronegative atom acquires a "partial“ charge. The partial charge is denoted with the symbol 8. Draw the partial charges on hydrogen fluoride. {3% .. “ ll -~ l: 1 Quick Quiz #2 Which of the following is NOT a polar molecule? (a) NaCl E 03) C02 E (C) NH3 (d) F2 (8) CH4 “‘5‘ E A dipole is 5 e Elam, E Dipole moment is a vector quantity. That is, it has a magnitude and a direction. E’i'cm GE; osL’A've «ME “55$“E CE‘MW E - For diatomic molecules, the molecular dipole is equal to the bond dipole. b all OK. it, _ ,th rm H _.. E: _ ’41 "" {\(i 'bschuect: parked, chmfis - For molecules with more than two atoms, bot the bond dipoles and the molecular shape must be considered in determining the molecular dipole. molecular dipole moment = vector sum of the individual bond dipole moments Remember: Lewis Dot Structures do not tell us anything about 3-D structure — however, this rule should be re-written as “When drawing Lewis Dot Structures, it is not necessary to depict the 3-D shape”. Water is bent! Quick Quiz #3 What does water's dipole moment look like now? lj f _. E Molecular geometry is the shape of a molecule. - ; We will use a model called the Valence Shell Electron-Pair Repulsion (VSEPR) model that is based on the repulsive behavior of electron- pairs. What technique do we know for drawing the valence electrons in a covalent molecule? Lupfi Tkt SthJEVes H 3 (Errata/«£3 How do we draw 3-D structures on paper CH‘i / i 041; or the black board? H H _. {rt Plains: .r.l74-—_:. .p-m will/ix. P043641?" fl : ovi— 042 Jr? “R M’h = this Molecular Geometry and VSEPR Chem P Lecture Handout Series #1 Valence Shell Electron Pair Repulsion Theory WSEPR) - gives us a 3-D idea of how molecules are structured Logic Behind Theory: What are electron rich . . regions? 1. around every central atom there are electron rich reg10ns b o hols 2. opposites attract, but like charges repel: each other \ lo h t P CLL r5 3. thus, valence electrons arrange themselves as a far away as possible. 5 Basic Arrangements [no lone pairs on central atom) 1. 2 electron richregions E Shape Type (C mav’ Examples: ' E # of dimensions 2. : bond angles l KOo 2. 3 electron rich regions Shape Type tn‘jonol Planar Examples: # of dimensions 1 For moichLL ‘clOlL Boron fitfluon‘rh bond angles no ° HZC o O Shape Type +cl~mk1drai Examples: # of dimensions 3 bond angles loci ,S a 3. 4 electron rich regions mulh‘pb. can LYGJ aims i i 4. 5 electron rich regions Shape Type hiaohal updram-Ja Examples: RDCI # of dimensions 3 5 bond angles 430 a} 90 ° 5. 6 electron rich regions Shape Type otl'akedml # of dimensions 3 bond angles a.“ “are“ 70° Molecular Geometry and VSEPR Chem P Lecture Handout Series #2 IMPORTANT CONCEPT: Bonding and lone pair electrons are not the same. Lone pairs take up more “space” Why? AT B A 3 Ig an 3' Pour are. umsle‘MA bu \‘uao “UCJLLJ Cr takes up less sPatte, Hun ir- Constrained ‘03 mo, hookaus \\_ Lewis Structure 3-D structure (VS PER) Shape type (Electron Pair _ Geometry) Molecular Geometry Bond Angle AXE Method (@1le A???” Ax '1? E n x 4A L X AX; Uneas- lriw 1;]. I I A x/ \x x/ij. ‘ MT AX, me. ngonaé planar Ben! «Angular '4' {WT fr; E/AHWX /1‘\""UX X \X X 523i X Ax. ms. Tmlmmafi, Trlgnrial mrmnkial “I; ? T “I; “‘29 F 7 XmAunltx 31%A.mllx jig/WK} " l “x X X axe, Mali. Trlgmal hlpwamidai Sawhorse o! Seesaw .3: \ XIII! !— xv!" l, x Pentagon-a! X i .H’!‘ .luxxf“? Xm...A..nuX\;:¢ "ix’ xffllf‘fixf 5's: AXQE; Square pyramidafi bipwamldal “UMBQY'CDO [ONE Pairs cu I—lc 1/ch stoF Cenlrml 0.5m somber 019 (L ocnols {alter-n5 bunch; I'D cenh'wl 0J3”) Ben! or Angular 151' X , 3H ,. ”iii: :\ “A up“; _: I ‘33ng X M382 T~shapu KunmAunilX: 1’3" W45“? MW; Squaw planar T-shape Liam" Multiple Central Atoms ° treat as individual central atoms meA-hmno L Ethylene C194 / w\'3onal planet! MOL 0166 ban “will; # of bonding and lone electron pairs are associated with specific molecular geometries ...
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