Chemical Bonding CHEM 101
Popular in Structural Chemistry, with Application to Chemistry of the Elements
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This 4 page Class Notes was uploaded by Piper Daniels on Tuesday October 13, 2015. The Class Notes belongs to CHEM 101 at University of Alabama - Tuscaloosa taught by Mrs. Leung in Summer 2015. Since its upload, it has received 30 views. For similar materials see Structural Chemistry, with Application to Chemistry of the Elements in Science at University of Alabama - Tuscaloosa.
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Date Created: 10/13/15
Chapter 6 Bonding Trigonal Planar Electron Geometry 1 3 electron gps all to bonding electrons atoms a mgegtrigonal planar 2 2 of 3 gps are bonds atoms M a egtrigonal planar b mgbent 0 ex N0239 d the lone pair pushes the other bonds to make an angle less than 120 degrees Tetrahedral Electron Geometry 1 4 electron gps all 4 are bonds atoms a egmgtetrahedral b ex CH4 0 1095 degrees between atoms 2 3 of 4 gps are bonds trigonal pyramidal a egtetrahedral b mgpyramidal 0 bond angles are less than 1095 degrees 107 degrees to be exact 3 2 of 4 gps are bonds atoms M a egtetrahedral b mgbent 0 bond angles are less than 1095 degrees 105 degrees to be exact Trigonal Bipyramidal Electron Geometry 1 5 electron gps all 5 are bonds atoms a egmgtrigonal bipyramidal three bonds that are on the same plane as the central atom equatorial two bonds that are one above and one below the central atom axial equatorialequatorial bond angles 120 degrees equatorialaxial bond angles 90 degrees 2 4 of 5 re bonds seesaw shape egtrigonal bipyramidal mgseesaw shape ex SF4 best position for the lone pair is in the equatorial position 90 degrees to two atoms instead of three if you were to take an axial atom e equatorialequatorial bond angles slightly less than 120 degrees f equatorialaxial bond angles slightly less than 90 degrees 3 3 of 5 re bonds Tshaped a egtrigonal bipyramidal b mgtshaped 60906 905 c lone pair is at an equatorial angle again d left with only two bond angles that are slightly less than 90 degrees e ex BrF3 4 2 of 5 are bonds Linear egtrigonal bipyramidal mglinear lone pair is in place of equatorial angle again bone angle between two bonds is exactly 180 degrees ex XeF2 09965 Octahedral Electron Geometry 1 5 of 6 are bonds souare pvramidal a egoctahedral b mgsquare pyramidal c bond angles are slightly less than 90 degrees d ex BrF5 2 4 of 6 are bonds sguare planar a egoctahedral b mgsquare planar c make sure you are putting the lone pairs on opposite sides of the atoms maximizing the distance between lone pairs i this puts all of the outer atoms in the same plane d 90 degree angles between bonds 3 3 of 6 are bonds tshaped a egoctahedral b mgTshaped c lone pair forces bonds to get closer to each other making the bond angles slightly less than 90 degrees 4 2 of 6 are bonds M a egoctahedral b mglinear c lone pair is on opposite of lone pair making the bond angles 180 degrees Larger Molecules 1 Some molecules have more than one central atom a Each with eg and mg 2 Atoms that are not a central atom can still have an eg but not an mg 3 Draw structures representing the shape 4 mg represents where the lone pairs are since chemists don t usually use them we will Polar or Nonpolar Molecules 1 remember as you go closer to Fluorine electronegativity increases 2 Nonpolar bond AEN s 04 a electrons are shared relatively equally 3 Polar bond 04 20 a electrons are not shared equally 4 Molecules can be polar or nonpolar a Depends on i polarity of individual bonds ii sum of these polar bonds iii overall molecular geometry mg Nonpolar Molecules 1 If all of the bonds are nonpolar the molecule is nonpolar a ex CZH6 ENC25 ENH21 CC AEN O CH AEN ENC ENH 04 All of the bonds are nonpolar Therefore nonpolar molecule 2 If the polar bonds cancel out the molecule is nonpolar a this means that the sum of all polar bonds O b must account for the molecular geometry c ex 002 ENC 25 ENO 35 CO larger EN minus smaller EN ENO ENC 10 polar bond value of the dipole vector is 10 it points towards oxygen these dipole vectors cancel out making a net dipole vector of 0 Therefore nonpolar molecule Polar Molecules 1 If there is only one polar bond there is nothing to cancel out with so the molecule is polar 2 If individual dipole bonds do not cancel out Summing Dipole Vectors 1 Linear vectors are on the same plane a same direction add them together b opposite directions subtract i equal in magnitude 0 ii different in magnitude point net dipole towards the direction of the larger vector 2 Two dimensional dipoles 90 degrees apart but same magnitude sum is between the two vectors 45 degrees dipoles 120 degrees apart but same magnitude equal to one of the vectors and in the center 60 degrees not the same magnitude net dipole will be closer to the larger dipole vector
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