Which one is the most polar molecule?

[TT0]

Homework Statement

Which of the following is the most polar molecule? ie. has the highest permanent electric dipole, CHCl3, SF6, SnCl4, BF3, CO2.

1. CHCl3
2. SF6
3. SnCl4
4. BF3
5. CO2

Homework Equations

The Attempt at a Solution

I chose CHCl3 because I think it is the only molecule that is non-symmetrical so will have a net dipole. Is this correct?

Cheers!

 

[James Pelezo]

You are right in choosing CHCl₃ but a more correct conclusion would be the molecule has a non-symmetrical (or, asymmetrical) distribution of charge creating a dipole moment. The structure is actually symmetrical with substrates attached to Carbon in a Tetrahedral Geometry. The dipolar nature comes from the high electronegativity of the three chloride substrates attached to the central carbon giving a strong partial negative charge to the chloride end of the molecule's geometry against a weak partial positive charge at the carbon - hydrogen end of the molecule. All of the other choices have symmetrical geometries and charge distributions about the given central elements.

b. SF₆ => Symmetrical octahedral geometry and charge distribution
c. SnCl₄ => Symmetrical tetrahedral geometry and charge distribution
d. BF₃ => Symmetrical trigonal planar geometry and charge distribution
e. CO₂ => Linear Molecule ( O = C = O ) with diametrically opposing polar bonds ( ⁺C = O^- ) with a net dipole = 0.

 

[TT0]

I see, thanks for the explanation!