Final answer:
To determine if a molecule is polar or nonpolar, look at Lewis structures and the molecular geometry. Nonpolar compounds are symmetric, while polar molecules are asymmetric, either containing lone pairs of electrons or atoms with different electronegativities. Knowledge of Lewis structures and VSEPR theory is crucial to understand molecular geometry.
Step-by-step explanation:
To determine if a molecule is polar or nonpolar, it is generally useful to look at Lewis structures. Nonpolar compounds will be symmetric, meaning all of the sides around the central atom are identical-bonded to the same element with no unshared pairs of electrons. Polar molecules are asymmetric, either containing lone pairs of electrons on a central atom or having atoms with different electronegativities bonded. This works pretty well, as long as you can visualize the molecular geometry. To know how the bonds are oriented in space, you have to have a strong grasp of Lewis structures and VSEPR theory. Assuming that you do, you can look at the structure of each one and decide if it is polar or not, whether or not you know the individual atom electronegativity. This is because you know that all bonds between dissimilar elements are polar, and in these particular examples, it doesn't matter which direction the dipole moment vectors are pointing (out or in).