Polarity

[Shanzey]

When labeling the dipole moment on a Lewis structure, how are we able to tell if the structure is polar or nonpolar? How are we able to tell if there is no net dipole?

[John Arambulo 1I]

You would know based on the electronegativity of the elements by using the periodic trends and also by formal charges because a negative formal charge would mean the electron density his higher around that atom.

[Maya Gollamudi 1G]

You can compare the electronegativity of the elements using the periodic table- there will be a greater electron density around the element with a higher electronegativity.

[Justin Quan 4I]

If you see that all the dipole forces cancels out, then the molecule is nonpolar. However, if there is a net dipole moment that's not zero, then you can tell that the molecule is polar.

[alex_4l]

Also, if the Lewis Structure contains all the same elements then the molecule is nonpolar, but if there is just one difference it can be polar.
For example, if there are 4 Cl attached to a centered Cl, that would have polar bonds but be a nonpolar molecule. But if there are 4 Cl attached to a centered C, that would have polar bonds and be a polar molecule.
It all really depends on the number of polar bonds--if there is an equal number of polar bonds, it's not polar, but if there is an inequality of polar bonds, it's polar.