ShmoopTube

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Here’s your Shmoop du jour, brought to by bond.

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Ionic bond. [James Bond taking glass of champagne]

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Taken, not shared.

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Consider the following molecule:

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And here's our question…

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According to VSEPR theory, what is the geometry of the hybrid orbitals on carbon in the molecule

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represented by the Lewis structure above?

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Here are our potential answers…

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So what is VSEPR?

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Voracious spies eat pizza regularly? [Man eating pizza slice]

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Very serious elephants pick radishes…. [Elephant eating radishes]

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No, unfortunately it has nothing to do with cool spies and elephants.

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VSEPR stands for Valence Shell Electron Pair Repulsion… [Valence and shell meet each other]

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…which is just a fancy way of saying that electrons in a molecule would rather not hang

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around each other.

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So what this question is actually asking is “what shape will put the electrons in this

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molecule as far away from each other as possible?”

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The electrons that we're worried about are the ones in the bonds and lone pairs around [Electrons orbiting in shell]

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the central atom.

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The central atom is exactly what it sounds like-the atom at the creamy center of the

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molecular candy bar. [Girl eating a lollipop]

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To find it, we have to find the atom bonded to the highest number of other atoms.

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In our molecule, the chlorines and oxygen have 1 other atom bonded to them and the carbon

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has 3 other atoms bonded to it.

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So carbon is the central atom of this molecule.

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We then count the number of lone pairs of electrons and bonds on the carbon in the Lewis [Carbon with electron pairs]

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dot structure.

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And…quick count, here…

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There are no lone pairs, which will make Valentine's Day much more tolerable this year… [Man and woman holding hands]

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…there are 2 single bonds…which…eh, there's always the day after Valentine's candy

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sale to look forward to…

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…and there's 1 double bond, which acts the same as a single bond when determining shape.

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What a player.

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Now let’s figure out what shape puts these bonds equally far apart; we don’t want to [Examples of various bonds appear]

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put two bonds far apart from each other just to find out we put them closer to the third

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bond.

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In order to figure this out, let’s pull out some dice. [Dice roll]

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Dice are a good way to visualize shapes with the bonds as far away from each other as possible,

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because dice have a regular geometry.

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Tetra means four…no not Tetris-close your other tab…and Octa means eight. [Person playing tetris]

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This means a tetrahedral shape is one with four sides and an ocatahedral shape has eight

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sides.

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If we look at our four sided die, it has four corners.

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The number of corners on our die is the number of atoms bonded to the central atom of the

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molecule that has that shape.

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Our central carbon is bonded to 3 things, not four, so the shape is not tetrahedral. [electrons appear by central carbon]

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Similarly, if we look at our eight sided die, we can count six corners.

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This means the central atom will have six things bonded to it in an octahedral shape,

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and our molecule only has three.

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So our molecule isn't octahedral.

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This rules out answers A and D Both trigonal planar and trigonal bipyramidal

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look similar and have tri in the name which, as we remember [Girl riding a tricycle]

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from our preschool days of tricycle riding, means three

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However, trigonal BIpyramidal has bi in it, meaning two; there are actually two pyramids [Man riding a bicycle]

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in the shape of this molecule.

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A trigonal bipyramid shape involves bonds to five different atoms, which our carbon

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doesn't have…

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Therefore, the answer must be C. Trigonal Planar.

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It's the most travelled airline of molecules [Trigonal planar aircraft flying]

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everywhere.

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