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PH3 is a non-polar covalent molecule. This is somehow confusing because, when you draw out the Lewis diagram, you will observe a lone pair on the P atom. However, if the electronegativity difference does not have a polar bond, then no matter what happens, it will always be non polar. In this case, the EN is 0.01, which indicates non polar. (Non polar EN is 0~0.4)

To decide whether a molecule is polar or non-polar, first draw the Lewis diagram. Then calculate the electronegativity. If the electronegativity is non polar, then no matter it has lone pairs or it has more than one group around the central atom, it will always be non polar. In this case, PH3 is non polar because of it has a non polar bond indicated by the electronegativity even though it has lone pairs.

But if the bond is polar, then you might have a chance to get a polar molecule depending on either of these 2 factors:

1. If there are lone pairs

2. If there are other groups around the central atom

For example, H2O is polar because:

1.It has a polar bond for electronegativity

2.It has lone pairs

(Even if it doesn't have a other groups around the central atom, it's still polar because it's polar if you just satisfy either of the 2 conditions)

If both conditions of the above are not met, then it's non polar even if it has a polar bond. Like CO2, a molecule has a polar bond, but fails to meet both of the conditions, is a non polar molecule.

Always remember to check your electronegativity. Remember if a molecule only has non polar bonds, then it must be a non polar molecule no matter which condition is satisfied after (ex. lone pairs). If a molecule has polar bonds, then it may be a polar molecule depending on either of the 2 conditions listed.

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12y ago

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