1 Molecular Polarity. 2 Polar Molecules Polar molecules are molecules that have a slightly positive...
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Transcript of 1 Molecular Polarity. 2 Polar Molecules Polar molecules are molecules that have a slightly positive...
![Page 1: 1 Molecular Polarity. 2 Polar Molecules Polar molecules are molecules that have a slightly positive end or pole and a slightly negative end or pole. The.](https://reader035.fdocuments.us/reader035/viewer/2022062517/56649f135503460f94c26952/html5/thumbnails/1.jpg)
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Molecular Polarity
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Polar Molecules
Polar molecules are molecules that have a slightly positive end or pole and a slightly negative end or pole. The molecule contains a dipole.
Physical properties depend on the polarity of a molecule.
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Polarity of a Covalent Bond
Electronegativity (EN) values are used to predict the polarity of covalent bonds. The greater EN, the more polar will be the bond. A polar bond has a dipole or slight separation of charge (from the unequal sharing of bond electrons).
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Polarity of a Molecule
The polarity of a molecule depends on the sum of all the bond dipoles (individual dipoles or vectors). If there is a net dipole for the molecule, than the molecule is polar. A molecule that has polar bonds may or may not be polar.
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Polarity of a Binary Molecule In binary molecules, the molecule
polarity simply corresponds to the bond polarity.
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Molecules with Non-polar Bonds
For example, dihydrogen molecule (H2) has a non-polar bond and thus is non-polar itself - the charge distribution is uniform across the molecule
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Molecules with Polar Bonds On the other hand, hydrogen fluoride (HF)
contains a polar bond and so it is a polar molecule. HF molecule has a concentration of negative charge (or greater electron density) near the fluoride (F) end of the molecule. The hydrogen end of the molecule has a concentration of a positive charge (or lower electron density). This reflects the fact that F atom is more electronegative than H atom.
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C OO
Molecular Geometryand Polarity
.. ..
H HO
+
Netdipole
In molecules containing more than two atoms, the shape or geometry of the molecule impacts the polarity.
Dipoles can cancel each other out resulting in nonpolar molecules.No Net dipole
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In general, a molecule is polarpolar if:
it is asymmetrical (isn’t a basic VSEPR shape) Ex:Ex: H2O, bent (polar)(polar) NH3, pyramidal (polar)(polar)
or if the terminal atoms/groups in a basic VSEPR shape differ.
Ex:Ex: CH2Cl2, tetrahedral (polar)(polar)
Molecular Geometryand Polarity
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Symmetrical Molecules
Molecules that exhibit symmetry in the distribution of electrons would have no net dipole. These molecules are considered non polar.
Non polarNon polarVSEPR shape
identical atoms
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Symmetrical Molecules
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Asymmetrical Molecules
Molecules that exhibit asymmetry in the distribution of electrons will result in a net dipole. These molecules are considered polar.
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Asymmetrical Molecules
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