CHE140 Lecture Notes 10.26 - 10.30
CHE140 Lecture Notes 10.26 - 10.30 CHE140
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This 5 page Class Notes was uploaded by Brittany Notetaker on Saturday October 31, 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 37 views. For similar materials see General Chemistry I in Chemistry at Illinois State University.
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Date Created: 10/31/15
CHE140 Lecture Notes 10262015 10302015 10262015 Lecture EPG Tetrahedral SN 4 has 4 sp3 hybrid orbitals EPG Trigonal Planar SN 3 has 3 sp2 hybrid orbitals and 1 unhybridized p orbital quot I OOO quotI o 1 sorbital 3 porbitals 3 sp3orbitals 1 unchanged A 3 3quot Trigonal Planar geometry EPG Linear SN 2 has 2 sp hybrid orbitals and 2 unhybridized p orbitals O gt I V l 75 I 39 3 3 n quot I 39 iquotv k l w u quotlgt According to Valence Bond Theory the first bond between two atoms is a sigma bond All others are pi bonds between unhybridized p orbitals quot l H CCH3R quotECch g NCHECHEN Q IfCHg CHg Q l 0 There are 12 sigma bonds 4pi bonds 22 lone pairs 0 There is always 1 sigma bond between 2 atoms 0 The rest of the bonds CO one bond is a sigma bond the other is a pi bond are pi bonds 0 Pi bonds are more reactive than sigma bonds Shape and Size Interactions 0 Molecular shape determines the chemical and physical properties of a molecule 0 Humans are dependent on these interactions because they form enzymes Enzyme 0 Has a pocket or active site of a specific shape size and polarnon polar areas Chirality o Chirality is the non superimposable mirror images like your hands 0 All amino acids besides one are chiral molecules 0 Any carbon with four different groups attached are chiral Delocalization o Resonance o Evenly spread out around the molecule 102815 Lecture Molecular Orbital Theory 0 Another way of looking at bonding in covalent compounds 0 Atomic orbitals combine into molecular orbitals o The number of atomic orbitals in is the number of molecular orbitals out 0 Oxygen 02 is paramagnetic o Paramagnetic has unpaired electrons o Diamagnetic has only paired electrons N He2s22p3 N 139 1L 1 1 1 15 25 21 N is paramagnetic because it has unpaired electrons Mg Ne3s2 Mg Ne TV 35 313 Mg is diamagnetic because all of its electrons are paired 02 appears to be diamagnetic when looking at the Lewis Structure but it is not Why 0 There are two types of molecular orbitals o Bonding hold the molecules together 0 Anti Bonding discourage the formation of bonds and breaks them apart Bonding Molecular Orbitals o Electrons in them stabilize the molecule 0 Have lower energy than starting atomic orbitals 0 Constructive interference AntiBonding Molecular Orbitals o Electrons in them destabilize the molecule 0 Have higher energy than starting atomic orbitals o Destructive interference 0 Anti b ondi ng O O O O o Bonding 10302015 Lecture Intermolecular Forces 0 IonIon Forces 0 Hold ions together in ionic solids E 1QLQ d o Cations and anions give negative Eel attraction o The larger the charge on the ions the stronger the ionion forces I 3 gt 2 0 The larger the ion size the weaker the ionion force Li Cl Strongest Eel ionion force Na Cl 1 K Cl Weakest Eel ionion force o The greater the charge the greater the insolubility 1 ions are more soluble than 2 ions Al3 N3 Q1Q2 9 Al3 F Q1Q2 3 Al3 02 Q1Q2 6 Which has the strongest ion ion attachment Al3 and N3 because their charges multiply to the largest number 0 Ion Dipole Forces g 5 5 HltH o The electrostatic attraction of an ion with the dipole of a polar molecule 0 This force is not as strong as an ion ion force 0 Intermolecular Forces in Pure Substances o 3 types I London Dispersion Forces Weakest I Dipole dipole Force I Hydrogen Bonds Strongest o Dipole dipole Forces magnets I Present in polar molecules I Electrostatic attraction of oppositely charged ends dipoles in molecules I The larger the dipole more polar the molecule the stronger the dipole dipole intermolecular force 0 Hydrogen bonding I A special very strong type of dipole dipole attraction I Occurs when hydrogen is bonded to O N and F I These are the three most polar bonds H can have and they are very directional