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Published byBlaise Reynolds Modified over 4 years ago

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Chapter 8 Shape of molecules

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VSEPR- Stands for: Valence-shell electron pair repulsion theory. States that pairs of valence e- arrange as far apart as possible.

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Ball-and-stick models- 3D physical model –ball = atom –Sticks/spring = single bonds –curved springs/more then one spring = multiple bonds.

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Bond angle- The geometric angle between 2 adjacent bonds in a molecule.

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Drawing 3D Single Double Triple Lone Pairs

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CH 4

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Common Shapes: –Linear -atoms connect in a straight line. –Lewis Dot Diagram:

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Common Shapes: –Bent molecules have a lone pair Involves O or S Lewis Dot Diagram: 104.5°

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Common Shapes: –Trigonal planar- triangular and flat shape. Involves B or Al –Lewis Dot Diagram:

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Common Shapes: –Tetrahedral –3 sided pyramid w/ four surfaces. Involves C or Si –Lewis Dot Diagram:

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Common Shapes: –Pyramidal -central atom bonded to 3 other atoms and has an unshared pair of valence e- Involves N or P –Lewis Dot Diagram: 107.5°

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All geometries in book w/ names and angles – section 8-1 Linear Tetrahedral Trigonal planar Pyramidal Bent 104.5° 107.5°

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Bond length- Down a group bonds lengthen Multiple bonds (double/triple) are shorter than single. Skagen’s HomepageChemistry Resources1 st slide

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Chapter 8 Shape of molecules

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8-2 Polarity Dipole- One side of a molecule has a negative charge and the other side has a positive charge Polarity- Is determined by the shape of a molecule and polarity of its bonds

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Polar Non-polar

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Determining Polarity

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Polar Non symmetrical Pyramidal and Bent are always polar - other shapes can be as well Symmetrical Linear, trigonal planer, and tetrahedral are possible non polar molecules Non-Polar

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Non-symmetric, Polar Symmetric, Non-polar

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If the molecule is: Covalent The bonds are polar. If the shape is Non-symmetric Symmetric The molecule is polar The molecule is non- polar Ionic or two of the same element

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