MOLECULAR POLARITY
Covalent Compounds  Elmhurst College
Electrostatic Potential Organic Functional Groups Functional Gps vs. Boiling Pt.  Chemistry Department
Simple Inorganics Organic Chain Length  Virtual ChemBook


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 Polarity of Simple Inorganic Compounds

Principles of Polarity:

The greater the electronegativity difference between atoms in a bond, the more polar the bond. Partial negative charges are found on the most electronegative atoms, the others are partially positive.

The molecular electrostatic potential is the potential energy of a proton at a particular location near a molecule.
Negative electrostatic potential corresponds to:
partial negative charges (colored in shades of red).
Positive electrostatic potential corresponds to:
partial positive charges (colored in shades of blue).

 Water is a polar molecule:

See graphic on the left. The bent geometry with the two lone electron pairs contributes to the effect. The electrostatic potential clearly shows that the oxygen is partially negative whereas the hydrogens are partially positive.

Water - Chime in new window


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Principles of Polarity:

The greater the electronegativity difference between atoms in a bond, the more polar the bond. Partial negative charges are found on the most electronegative atoms, the others are partially positive.

The molecular electrostatic potential is the potential energy of a proton at a particular location near a molecule.
Negative electrostatic potential corresponds to:
partial negative charges (colored in shades of red).
Positive electrostatic potential corresponds to:
partial positive charges (colored in shades of blue).

Ammonia is a polar molecule:

See graphic on the left. The trigonal pyramid geometry with the one lone electron pair contributes to the effect. The electrostatic potential clearly shows that the nitrogen is partially negative whereas the hydrogens are partially positive.

Ammonia - Chime in new window

 Hydrogen Chloride is a polar molecule:

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The linear geometry with two different non-metals contributes to the effect. The electrostatic potential clearly shows that the chlorine is partially negative whereas the hydrogens are partially positive.

Hydrogen Chloride - Chime in new window


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Methane is a non-polar molecule:

See graphic on the left. The tetrahedral geometry with the contributes to the effect.This is a symmetrical molecule with electronegativities of the carbon and hydrogen almost the same with carbon just slightly higher. The electrostatic potential clearly shows that the carbon is just very slightly negative (small red spot) whereas the hydrogens are very slightly positive. The overall effect is an almost completely gray color of the electrostatic potential surface which is neutral or non-polar.

Methane - Chime in new window

Oxygen is a non polar molecule:

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The linear geometry with two identical non-metals contributes to the effect. There are no partial charges since the electronegativities are identical. The electrostatic potential clearly shows an overall gray color which is neutral and typical for a non-polar molecule.

Oxygen - Chime in new window

Carbon Dioxide is a non polar molecule:

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The linear geometry with two identical oxygen atoms attached to a center carbon gives rise to a special effect. The molecule is symmetrical. There are partial charges seen from the difference in the electronegativities. The electrostatic potential shows a blue (partially positive) color for carbon and shows a red (partially negative) color for both oxygen atoms. However, the symmetrical nature of the bonds has the overall effect of canceling the dipole, therefore the molecule is non-polar.

Carbon Dioxide - Chime in new window