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