Question

How do I know if a molecule is polar or nonpolar?

Answer 1

The polarity would depend usually if there is a electronegative atom.

If there is like in water for example where the oxygen is electronegative then the molecule would become polar.

If it is a molecule like ethane then the molecule will be non polar since there are no electronegative atoms in the molecule.

Answer 2

thanks

Answer 3

electronegative atoms are for example all the elements in the group 7 of the periodic table. (F, Cl, Br, I)

There are others such as O and N as well.

Answer 4

To add some info provided by Christina. A molecule will be polar IF there is a difference between the electronegativity of the central atom and the other atoms attched AND if it is not a symmetrical molecule. Almost all atoms have a difference in electronegativity (EN), even C and H to form CH4. The C-H bond will be polar since C has an EN of 2.4 and H has EN of 2.1; thus, the C will be the negative end and H will be the positive end of four polar C-H bonds of the CH4 molecule. The molecule, however, will NOT have a dipole moment because it is a tetrahedral molecule and each of the individual C-H polar bonds are canceled out. The same thing happens for the CO2 molecule, which is O=C=O. Each O=C or C=O is polar (C is 2.4 EN and O is 3.5 EN) BUT the molecule is linear and the two individual polar bonds cancel each other and the CO2 molecule, as a whole, has no dipole moment. In fact, that is how we know H2O is NOT a linear molecule. H2O HAS a dipole moment; therefore, it can't be linear.

Answer 5

wow Dr.Bob

My explanation was nothing compared to yours. Even I learned a few things from your explanation. Especially your explanation of how we know that H20 is not a linear molecule.

Answer 6

Thanks Christina. Everything you said in your answer was correct. Remember I've been at this longer than you

Answer 7

Yes I know..hopefully I'll know as much later.