CHE140 Lecture Notes 10.19 - 10.23
CHE140 Lecture Notes 10.19 - 10.23 CHE140
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This 12 page Class Notes was uploaded by Brittany Notetaker on Saturday October 24, 2015. The Class Notes belongs to CHE140 at Illinois State University taught by Dr. Chris Hamaker in Summer 2015. Since its upload, it has received 38 views. For similar materials see General Chemistry I in Chemistry at Illinois State University.
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Date Created: 10/24/15
CHE140 Lecture Notes 101915 102315 Exceptions to the Octet Rule 1 An odd number of 6 overall 0 The atom With the lowest electronegativity gets the odd electron and is therefore short of an octet QEQ Q 2 Boron usually has less than an octet i i 9 H DIR E H H I in i1 B H o BH3 has 6 valence electrons 3 An expanded octet has more than 8 electrons 0 Only elements With equal to or more than the atomic number of 12 0 Elements 12 P C I Phosphorus Pentachloride quot 02 5 I O 5 1 s P CQ ace 0 P has 10 valence electrons 0 Expanded octets usually only expand to 10 or 12 valence electrons g C 0 FeF on 0 g 00 E o Xe has 12 valence electrons Xe Xeno39 tr uoride Bond Length and Bond Strength Bond Length pm BDE kJrnol C O 143 358 C O 123 743 C O 113 1072 0 Bond Dissociation Energy H Longest lengtl weakest energy i H C o H w H Shortest lengtl strongest energy Estimating AH using BDE s Aern ZAHbreaking 39 ZAHforming C2H4 302 9 2C02 2H20 Breaking 4 Broke HX 4 C H bonds i I 1 CC bond C 1C 3 00 bonds H I l Making 0 4 C20 bonds i 4 O H bonds I I HOH II Aern 4C H 1CC 300 4CO 4O H 4413 kJmol 614 kJmol 3495 kJm01 4799 kJmol 4463 kJm01 Aern 1297 kJmol exothermic Chapter 9 Shapes of Molecules C02 0 i I I 0 C02 is linear 0 C SN 2 S02 E f H Ej 0 SOzisbent 0 SSN3 Valence Shell Electron Pair Repulsion Determines the shape Electron Pair Geometry Parent Geometry o EPG is the positions of lone pairs and atoms 0 Determined by the steric number SN Molecular Geometry Shape o Determined by the positions of atoms SteriC Number SN SN of lone pairs of atoms bonded 102115 Lecture A central atom X bonded atoms E lone pairs SN 2 EPG Linear 0 MG linear V O C 1 0 SN 3 EPG Trigonal Planar 0 3 atoms 0 lone pairs AX3 0 MG trigonal planar H H H 1200 angle between bonds 0 2 atoms 1 lone pair AXzE 0 MG bent S f H jf j39 I A little less than 1200 between bonds Lone pairs occupy more space than bonding pairs Multiple bonds occupy more space than single bonds Lone pair gt Double bond gt Single bond SN 4 EPG Tetrahedral 0 3 atoms 1 lone pair AX3E 0 MG Trigonal Pyramidal o o I I Bond angles are approx 10950 0 2 atoms 2 lone pairs AX2E2 0 MG Bent 36quot quotoquot O 0 pl SN 4 EPG Trigonal Bipyramidal 0 5 atoms 0 lone pairs AXS 0 MG Trigonal Bipyramidal q 0 4 atoms 1 lone pair AX4E 0 MG See saw II F Ii i II I l i i F art F i i l i quot i I F 1 H II 0 3 atoms 2 lone pairs AX3E2 0 MG T shaped P1 b I I i G I 0 2 atoms 3 lone pairs AX2E3 0 MG Linear oo 00 o 00 O SN 6 EPG Octahedral 0 6 atoms 0 lone pairs AX6 0 MG Octahedral F ll Bond angles are 900 0 5 atoms 1 lone pair AXsE 0 MG Square Pyramidal F IFS fI Iodine Penta uoride o o 0 4 atoms 2 lone pairs AX4E2 0 MG Square Planar rxeF I Polar Bonds and Molecules 0 Polar bonds have a bond dipole 0 One slightly positive end one slightly negative end 0 Polar molecules have a molecular dipole 9 one end positive one end negative 0 Molecules whose ends have the same charge are not polar Polar Molecules Need 1 At least one polar bond 2 Asymmetry a A lone pair on the central atom I More than one type of atom on the central atom S f H f 102315 Lecture Polar and Non Polar Molecules Atom Electron C 25 H 21 Cl 30 N 30 l N gl 21 AEN O The electronegativity between N and Cl is the same Non polar bonds Non polar molecules H I39T39I H H AEN Polar bonds Polar molecules 39i il ij il C I C HAEN04 C CIAEN05 Vibratin Bonds and the Green House Effect Earth39s Greenhouse Effect Greenhouse gases let the sun s short wave radiation visible light reach the earth but trap some of the long wave infrared or heat radiation coming from the warm earth Incoming solar radiation Reflected by the short wave 9mm and its Infrared radiation atmosphere heat emitted from earth39s surface long wave Atmosphere Carbon Store mmhare E B l Solar radiation strikes the surface and heats it up through absorption With the surface heats up it emits IR radiation 3 Molecules can absorb IR radiation which causes bonds to Vibrate and increase their kinetic energy therefore they give off heat Warms the earth39s surface 591 0 Without the greenhouse effect Earth s surface would be about 18 C 0 The actual surface temperature is about 15 C o The main gases that absorb the IR radiation and heat up the surface temp are H20 CH4 C02 and CFC s o In order to absorb IR radiation 0 The compound must have polar bonds 0 Vibrations must change the molecular dipole Valence Bond Theory 0 Bonds are formed from the overlap of valence atomic orbitals 0 Sigma bonds the orbitals overlap between the nuclei SS 0 Pi bonds the orbital overlap does not occur between the nuclei but above and below the nuclei PP 0 of atomic orbitals 0 Atomic orbitals miX and average Tetrahedral EPG 9 sp3 hybridization 10950 angles ll all hybridization T T Spa energy 1 SP3 hybrid orbitals have one s orbital and 3 p orbitals Trigonal Planar EPG 9 sp2 hybridization 1200 angles C uc n v 1 1 J at p l c pivr c y 39 Electronic Cm gtnation of C 1T H T T l In gr Quad state Electronic co gLH39athll of C LT T 7 l A In an cuted state i 5 1 hybrldIzatnjr I If C ll l l l l 1 I Three 3955 unhybx Mixed t r39brldlzed Orbit3 orbatals SP2 hybrid orbitals have three hybridized sp2 orbitals and one unhybridized p orbital Linear EPG 9 sp hybrid 1800 angles it 1 i t t t hybridization T Spa energy 1 0 SP orbitals have two sp hybridized orbitals and two unhybridized p orbitals Hybrid orbitals make sigma bonds Unhybridized orbitals make pi bonds
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