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how to work out dipoles?

Hi i was wondering if anyone could explain to me how to work out whether a molecule has a dipole and explain the 'symmetrical molecules cancelling out the polarities thing' please?
Reply 1
Avatar for Interea
Interea
19
Permanent dipoles occurs when the two atoms involved in a covalent bond have different electronegativities (power to attract the electron density in a covalent bond). The more electronegative atom will attract the electron density of the bond, making it partially negative and the other atom partially positive.

However, when you have symmetrical partial charges, the polarities are cancelled out. Take, for example, CO2: the carbon atom is partially positive, and both oxygens are partially negative. Since the molecule is linear and partially negative at both ends, this means no end of the molecule is more negative than the other, so there is no permanent dipole.
Reply 2
Avatar for Moni1234567
Moni1234567
OP
5
Original post by Interea
Permanent dipoles occurs when the two atoms involved in a covalent bond have different electronegativities (power to attract the electron density in a covalent bond). The more electronegative atom will attract the electron density of the bond, making it partially negative and the other atom partially positive.

However, when you have symmetrical partial charges, the polarities are cancelled out. Take, for example, CO2: the carbon atom is partially positive, and both oxygens are partially negative. Since the molecule is linear and partially negative at both ends, this means no end of the molecule is more negative than the other, so there is no permanent dipole.



thank you, could you also explain then how ClF3 has a dipole as they both have similar electronegativities? Is it because of the lone pairs??
Original post by Moni1234567
thank you, could you also explain then how ClF3 has a dipole as they both have similar electronegativities? Is it because of the lone pairs??


Yes it is to do with the lone electrons. All pairs of electrons will repel one another, spacing out the bonds. If there are lone electrons, however, they are spaced out in a bonding position if that makes sense. So (without researching it) I assume that ClF3 must be a tetrahedral shape, and the electronegativity of the fluorine atoms is concentrated at one end. Therefore the Cl atom is slightly positive in comparison.

Does that actually make sense? I hope I’m getting at the right thing!

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