Chem 1211 1st Edition Lecture 23 Outline of Last Lecture I Octet Rule II Geometry III Electronegativity Outline of Current Lecture I Geometry Continued II Electronegativity continued Current Lecture I II Geometry Continued a ConcepTest What are the electron pair and molecular geometries for PCl5 i Octahedron trigonal bipyramid ii Trigonal bipyramid tetrahedron iii Tetrahedron trigonal pyramid iv Trigonal pyramid bent v None of these 1 ANSWER None of these 2 REASONING P has 5 single bonds and no lone electron pairs It is trigonal pyramid but not bent b Which pair of atoms would be predicted to have an ionic bond based on electronegativity values i N Cl ii P Cl iii N F iv Cl Na 1 ANSWER Cl Na Electronegativity a Bonds i Equal sharing electronegativity 5 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute b c d e f g h ii Polar covalent electronegativity 7 1 8 iii Ionic electronegativity 2 Opposite charges attract Fluorine molecules 4 0 electronegativity will float around randomly they will not be pulled in a certain direction Measure Charge Separation i Experiment values ii Dipole moment has two connected poles one with a charge and one with a charge iii Bigger dipole bigger charge separation iv Dipole moment u charge x distance v Look up in table ConcepTest Which molecule DOES NOT have a dipole moment i CH4 ii CH3F iii CH2F2 iv CHF3 v CF4 1 ANSWER CH4 2 REASONING The answer is not CF4 because fluorine makes it polar Polar bonds components Dipole moments molecular i BF3 planar polar bonds pull with the same force in 3 different directions Using basic principles which double bond would you expect to be the long C C C O C N i C C ii C O iii C N 1 C C because C has the biggest radius look at periodic table trends
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