Book Problems 2E.25

[Esther Kim]

The chemical structure CCL2H2, couldn't it be nonpolar if the CL's were on opposite sides? Why is the right structure in the book the structure in which the Cl's are next to each other?

[Natalie Keung 1D]

Actually in any configuration, CCl2H2 cannot be nonpolar. The shape of this molecule is tetrahedral since there is a central carbon and 4 outer atoms. This means the bond angles would be 109.5 degrees. If there are two Cl's across from each other, they would not be 180 degrees from each other, which means their dipole moments would not cancel.

[RossLechner3E]

Make sure when you draw out the shape of the molecule you use its VESPR 3D shape. One can use the Lewis Structure to visualize the bonds and basic idea, but should not draw any conclusions about polarity for example, given in this, the Lewis Structure would lead you to believe it will be polar, but using the VESPR tetrahedral model we know it cannot be polar because the vectors will cancel.

[Anubhav_Chandla1G]

If the chemical 3-dimensional structure of CCl2H2 is drawn out, it has 4 elements that surround a central atom. Due to the bond angles being 109.5, if vectors are drawn for each element towards the central atom, the vectors will cancel out, leading to a compound that will always be polar.

[Ishant Goel 2D]

I think there is an easier way to determine if it's nonpolar or not. You first see if the lewis structure has any lone pairs, and if it does, it has to be square planar or linear. This structure is tetrahedral with no lone pairs so it passes the first test. The second test is to see if all the peripheral atoms are the same. In this case, they are not the same. CCL4 or CH4 would be nonpolar but CH2CL2 is polar because the peripheral atoms are different.