Unmixed AOs

From WikidChem

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Slide 38

Unmixed Valence Atomic Orbitals This slide simply illustrates what the previous slide (37) was trying to explain. When you introduce a positive charge (H+), the electrons are stabilized and thus the energy is lowered: low LUMO. When you introduce a negative charge (OH-, CH3-), the opposite occurs, as now the electrons have more potential energy as they are trying to get away from each other. Energy goes up, and thus: high HOMO. For NH3, OH2, and BH3, we focus on the lone pairs, which have not interacted with anything and thus are unmixed. (I'm actually a little unclear as to how this affects energy however.) -ECM

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Slide 39

Acid Base Reactions Basically, this slide is introducing a new notation: curved arrow notation. The base of the arrow starts on the location of the electron pair originally. Then the arrow goes to where the electron pair moves to. Pretty straightforward. Let's go through the examples: H2O: we begin with the hydrogen and hydroxide ions. The extra pair on hydroxide moves toward the bond and we form water. NH4: we begin with the hydrogen ion and ammonia. The extra pair on ammonia moves toward the bond and we form ammonium. but realize that since we took electrons from an uncharged ammonia, now it is positively charged, hence the big + on top of the nitrogen in ammonia. the other two just follow the same pattern. -ECM