Why is CH2Cl2 polar?

[Ananta3G]

In question 2.25 in the textbook, it says CH2Cl2 Is polar - why? In the answers, it shows the lewis structure diagram with the Hs next to each other and the Cls next to each other which would cause an uneven distribution of charge so it makes sense that it would be polar, but how would I know to arrange them like that vs opposite each other? Thanks!

[alicechien_4F]

The Cl atom has a much higher electronegativity than H and has more electrons in its valence shell (8 vs. 2) after bonding, so there will be a stronger negative charge on that end of the atom. Hope this helps!

[EmilyJoo_1G]

It's polar because Cl has a delta negative charge due to its negativity, which means it would cause a temporary polarization of electrons of atoms around it.

[LNgo 1G]

I think the electron repulsion plays a part in orienting the molecule so that the chlorine atoms are not on opposite poles as you might expect, but they are placed next to each other in the molecular structure.

[Indy Bui 1l]

You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be opposite of each other, but in actuality they will always be next to each other in the 3d plane, no matter how u orient them.

[KBELTRAMI_1E]

You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be opposite of each other, but in actuality they will always be next to each other in the 3d plane, no matter how u orient them.

how do we know they are next to each other?

[Rory Simpson 2F]

You should think of this molecule in the 3d form. In a tetrahedral, no matter where you put the atoms the Chlorine atoms will always be next to each other. I can't Draw a picture on here, but just look one up it might be helpful. The lewis structure looks like u can orient the chlorines to be opposite of each other, but in actuality they will always be next to each other in the 3d plane, no matter how u orient them.

how do we know they are next to each other?

If you look at the VSEPR molecular structure, the molecule is tetrahedral. Every atom bound to the central atom is next to each other because of the positions of atoms in that arrangement.

[Eva Zhao 4I]

To add on, typically speaking, a molecule with a tetrahedral shape is only nonpolar if all four atoms bonded to the central atom are the same.

[Justin Quan 4I]

To add on, typically speaking, a molecule with a tetrahedral shape is only nonpolar if all four atoms bonded to the central atom are the same.

This is because different atoms have different electronegativity. Thus, each atom surrounding the central atom will have a slightly different attraction to the electrons, which will produce a net dipole dipole force.

[ranqiao1e]

Because the Cl is much more electronegative than carbon

[Bradley Whitworth 4B]

When you add all the dipole moments taking into account shape you get a overall dipole moment so it is polar.

[erica thompson 4I]

I always find it's easier to think about it visually! I would recommend drawing the Lewis structures, and more importantly the molecular structures, and drawing arrows toward the molecules with more negative charge. Think about the trajectories of the arrows you're drawing!

[Noah Canio 3C]

If you were to consider the molecule as a 3D shape as opposed to a 2D one, then it's possible to see that the chlorine atoms and the hydrogen atoms are not exactly opposite of each other, which a potential lewis structure would suggest. Because these atoms are not on opposite ends, their dipole moments don't cancel each other out, leading to CH2Cl2 to be a polar molecule.