To determine if CH2Cl2 (dichloromethane) is polar or nonpolar, we need to first determine its geometry. This presumes knowing the rules for drawing a correct Lewis structure and you can find more details about Lewis structures here.
Carbon is the central atom:
There are 4 + 2 + 2×7 = 20 electrons, and 8 have been used to make four bonds. The remaining 12 go on the two chlorines as lone pairs:
The central atom has four atoms and no lone pair, therefore, both the electron and molecular geometries are tetrahedral:
Now, the polarity: The first thing here is to determine if the C-Cl bond is polar. Depending on the difference in the electronegativity values, covalent bonds can be polar and nonpolar.
- If the difference in electronegativity is less than 0.5, the electrons are about equally shared between the two atoms, forming a nonpolar a covalent bond.
- If the difference in electronegativity is between 0.5 and 1.7, we have a polar covalent bond.
- A difference of 1.7 or higher is so large that the electrons are no longer shared, and an ionic bond is formed. Ionic bonds are formed between metals and nonmetals.
The C-Cl bond is polar, and the four bonds are not equivalent, which results in an asymmetrical distribution of bonding electrons in the molecule. Therefore, CH2Cl2 is polar and the overall permanent dipole is directed toward the two C-Cl bonds as drawn:
Remember, the net dipole of the molecule is the vector sum of all the dipoles and here it equals zero because the bonds are equivalent and pointing in opposite directions.
Check this 99-question multiple-choice quiz on Geometry and Hybridization:
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