lecture 2 chem 6ah

lecture 2 chem 6ah - Lewis structure the duel rule and...

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Q: in which case is Ed the most appro.? 1. Nacl 2. CaBr2 3. Ali3 3, b/c polorization, creates more covalent chara. Covalent bonding - atoms of similar electronegativities share electrons and form molecules- this is what molecule is. - chara. bonds according to length, energy and order - C -- C is about the same length, if it changes, there's something going on. - Bond Length: distance b/w 2 bond nucleii - bond length increases w/ Z (atomic #, or nuclear charge) - bond length decreases as bond order increases - Bond Energies: E req'd to break a bond; - bond forms b/c there is net stabilization - Bond desociation energy, energy is about positive, b/c you always need energy - As z goes up, the bond energy goes down - stable bonds = large values - BDE or Ed: BE decreases with increasing Z - Bond order: # of shared e's b/w 2 given atoms - As bond discoociaton energy goes up, bond length goes down
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Unformatted text preview: Lewis structure:- the duel rule and actet rule- Estimate "Correctness" of Lewis structure 1. More covalent bonds, more stable and therefore better the structure 2. Charge separation (the more charge is present in the lweis structure, the less stable it is) will descrease stability 3. When the one with the fact that all atoms have an octate, those structure where all atoms have an octet will be the best ones 4. fewest amount of charge - best (minimization of charge is best) Bond length is not what we expect them to be Rules of resonance structure- resonance is only a theory!- all structure must be proper Lewis structures- All structure must have the same number of unpaired electrons (if any)- Delocalization - the ability of spread the e's- The actual energy of the molecules is lower than any resonance contributor- Only electrons can be moved (pi and I.p)...
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This note was uploaded on 09/28/2011 for the course CHEM Chem 6AH taught by Professor Hoeger during the Fall '08 term at UCSD.

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