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18 Cards in this Set
- Front
- Back
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VSEPR theory
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Valence shell electron pair repulsion theory (electron pairs repel each other)
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Linear
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2 groups---2 atoms
180 degrees |
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Trigonal Planar
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3 groups---3 atoms
120 degrees |
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Tetrahedral
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4 groups---4 atoms
109.5 degrees |
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Bent
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4 groups---2 atoms, 2 lone pairs
approx. 109.5 degrees |
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Trigonal Pyrimidal
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4 groups---3 atoms, 1 lone pair
approx. 109.5 degrees |
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wedge
dashed line |
-bond in front
-bond behind |
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electronegativity
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a measure of an atom's attraction for electrons in a bond; how much a particular atom wants electrons
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electronegativity trends
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electronegativity:
-increases across a row -increases up a column |
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electronegativity values determining polarity of bonds
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nonpolar: 0.4 units and lower diff
polar: 0.5-1.9 units ionic: above 1.9 |
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Symbol S-
Symbol S+ |
more electronegative atom
less electronegative atom |
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Molecule contains zero or one polar bond----->
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-a molecule with no polar bonds is a nonpolar molecule
-A molecule with one polar bond is a polar molecule |
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Molecule contains two or more polar bonds------>
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1. Identify all polar bonds based on electronegativity differences.
2.Determine the shape around individual atoms by counting groups. 3.Decide if individual dipoles cancel or reinforce. |
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Covalent compounds that have more than one polar bond
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-If the individual bond dipoles do not cancel, the molecule is polar.
-If the individual bond dipoles cancel, the molecule is nonpolar. |
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dipole
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a separation of charge
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direction of arrow
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points toward the more electronegative element.
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example: is H2O polar?
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-yes, because H2O is bent and the H atoms point toward the O atom, which means that the 2 H dipoles reinforce
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When do dipoles reinforce?
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-if all are pointing towards central atom, they do.
-if all are pointing in opposite directions, away from central atom, they cancel. -if two are going in same direction, away from central atom, they reinforce. -in a linear molecule, if the arrows both point away from the central atom, they cancel. |
