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lecture3_5a - Summary of Critical Points from Last Class...

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1 CHECKLIST for Drawing a Legitimate Lewis Structure 1. Correct TOTAL number of valence electrons add or take away electrons to account for – or + net charge (ion) 2. Sum of the valence electrons around each… H atom is two N, O, or F atom is 8 C atom is usually 8 (but sometimes 6… a “ carbocation ”) 3. All non-zero formal charges must be shown (usually –1 and +1) Summary of Critical Points from Last Class Summary of Critical Points from Last Class +1 0 - 1 C C Z Z Z Note: The two other ways to draw a carbocation are very uncommon. C Z Z Z Z Z C Z Z C Z Z Z C Z C Z Z Z Z C Z C Z N Z N Z Z N Z four ways ( draw the two that are missing ) draw three ways draw two ways O draw three ways draw two ways draw one way X Z X Z X Z two ways (less common) draw one way draw one way (an anionic atom) Preview of this Class Today we will learn about s and p orbitals and that a bond can be described as an overlap of two orbitals z axis y axis z axis y axis x axis z axis y axis x axis z axis y axis x axis 2s 2p x 2p y 2p z Nucleus of atom s ” orbital ( s pherical) Possible path of an electron in an s orbital p ” orbital (double p ear shaped) Possible path of an electron in a p orbital Node (plane where electron cannot be found) 90% chance of finding electron inside this sphere 95% chance of finding electron inside this larger sphere Think of an orbital as the “home-base territory” of an electron Preview of this Class What is an electron orbital ? Begin Work on ChemActivity 3 Clicker question(s) covering the first two pages ~8 minutes
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2 Play-dough Demo #1 z axis y axis z axis y axis x axis z axis y axis x axis z axis y axis x axis 2s 2p x 2p y 2p z 2 Mix all 4 orbitals together z axis y axis x axis Play-dough Demo #1 z axis y axis z axis y axis x axis z axis y axis x axis Cut into four equal pieces (they don’t look equal because it is a 3D perspective drawing) 2 Arrange so point to four corners of a tetrahedron Each piece is called a hybrid orbital (hybrid = mix of s and p) Each hybrid orbital has a small 2 nd lobe—the result if its “p orbital character”. For simplicity, we will ignore this small lobe, and focus on the main lobe for now. 1 Play-dough Demo #1 Which are possible identities of the following neutral molecules shown as orbitals? CH2 , CH4, CH3 B e H 2 , N H 4 , B H3 H2 O , CH 4 , N H 3 t he a bov e w or k one of th e a b ove Not sure N eed m or e time 3% 2% 84% 2% 4% 0% 5% 4 = pair of electrons 1. CH 2 , CH 4 , CH 3 2. BeH 2 , NH 4 , BH 3 3. H 2 O, CH 4 , NH 3 4. All of the above work 5. None of the above 6. Not sure 7. Need more time
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3 Bond Angle 109 o barb2right sp 3 hybridized O H H O H H ~109 o H C H H H ~109 o N H H H N H H H ~109 o Play-dough Demo #2 z axis y axis z axis y axis x axis z axis y axis x axis z axis y axis x axis 2s 2p x 2p y 2p z z axis y axis x axis Play-dough Demo #2 z axis y axis z axis y axis x axis z axis y axis x axis Save one p orbital for a special use Orbitals in the 120 o Hybrid Orbital Set Arrange hybrid orbitals in trigonal plane (120 o apart)
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