Molecule Polarity And Bigger Lewis Structures: Fill & Download for Free

To answer a question of this type, you must understand that intermolecular forces are attractive forces of different intensities and durations based on the polarities or lack of permanent polarities of the involved molecules. So, you must first figure out whether the molecules in question are polar.To figure out if a molecule is polar, you must draw a Lewis structure, the figure out the shape of the molecule, and the electronegativity differences of each bond of the central atom.So, to draw a Lewis structure, there are a couple of different methods, and some teachers are particular about which method you use. Generally, there will be a page or two in your textbook that give the steps involved. Basically, both methods need you to count the valence (outer shell) electrons of each atom in the structure. Then determine (or be told) the identity of the central atom, place it in the center, attach the other atoms by single bonds, and distribute the other valence electrons according to specific rules. If there aren't enough electrons to give each atom the number of bonds it needs, you follow rules to make multiple bonds.In CBr4, the carbon is central, and has four single bonds to each bromine, and each bromine has three pairs of non-bonded electrons.Now, you need to figure out the shape of the molecule. If a central atom has four bonds and no line pairs, the shape around the central atom is tetrahedral.Now, you need to figure out if the entire molecule is polar. To do so, you must first determine if the bonds themselves are polar. To do that, you look up the Pauling electronegativity of each atom involved in an individual bond, and subtract the smaller one from the larger. If the electronegativity difference is less than 0.4 (some books use 0.5) the bond is non-polar. If all the bonds are non-polar, then the molecule cannot be polar. If the electronegativity difference is between 0.4 and 2.0, the bond is polar covalent, and if bigger than 2.0, the bond is ionic. Now, if there is at least one polar bond, there's a possibility that the molecule is polar. To determine if it is, look at the structure. If the central atom is surrounded by completely symmetric atoms, then the molecule will be non-polar. If the central atom is surrounded by an asymetric arrangement of polar bonds, the molecule will be polar.So, now, to do this particular problem, draw the Lewis structure, determine the shape, calculate the electronegativity differences, and determine if the area around the carbon is completely symmetric.If the molecules are all non-polar, the only intermolecular forces are the dispersion forces (also known as induced dipole effect, hydrophobic effect, Van der Waals forces, and there are other names). If the molecule has a permanent dipole but doesn't have N-H, O-H, or F-H bonds, then the IMF would be the dipole-dipole effect, and if it does have those three special types of polar bonds, then the IMF is called hydrogen bonding (even though it's not really a bond.)If you still don't understand, write back and I'll try to explain better.

Yes, SO2 is a polar molecule. Here’s why:To determine the polarity of a molecule, the first thing that should be done is to take a loom at its lewis structure.This is given below:As you can see here, the molecule has a central sulfur atom that is bonded with two oxygen atoms and has two lone pairs of electrons.The next step from here is to determine its molecular geometry. In this case, the SO2 molecule is what is known as “bent”. This is because in general, electrons want to stay as far apart from each other as possible. But because the lone pair of electrons is repelling the two bonds, they are skewed down resulting in a bent shape.The last, and possibily most relevant, concept important for determining the polarity of the molecule is electronegativity. All atoms have an electronegativity, or a tendency to attract a shared electron. Because oxygen is a smaller molecule, its nucleus has greater force of attraction on the shared electrons between it and sulfur. Sulfur, on the other hand, is bigger, so its nucleus has less of a pull on the shared electrons. This is most easily described with Coulomb’s law equationThe equation describes to us that as r(the distance between to electric forces) decreases, the electric force between them increases. This proves why oxygen has the higher electronegativity.Now, because oxygen has a stronger pull on the electron in the bond betweem S and O, the result is a dipole moment, which can be seem more easily using vectorsIt is clear here that the electrons are being pulled closer to the oxygen atom. This results in a partial negative charge on the oxygen and a partial positive charge of the sulfur. THIS IS THE KEY. The separation of these partial charges causes a dipole moment. This is what makes SO2 a polar molecule. But then, why does the shape of the molecule matter?Well, in certain cases, even if the bond is polar, the molecule is nonpolar. This is most commom in linear shapes like CO2.I hope this helps clear up the concept of polarity for you.

Geometry makes it polar. In order to see this you simply need to draw the lewis structure for the molecule and look at it. If you had for instance CF4 it wouldn’t be polar since it is symmetrical in every direction. So the easiest way to see this is lewis structure.Let’s make a lewis structure then. First thing we do is count the valence electrons. C(4), O(6),F(7), if we sum it up we get 4+6+2*7=24. The central atom is C. Then there is the octet rule which says that the side atoms need to have 8 electrons around them (exception can be H which can only have 2). So now we can make a rough sketch. This should be the thought process.As you can see in the last picture now if we just focus on polarity the symmetry isn’t the same in every direction. As you can see O has only 2 non-bonding electron pairs, F on the other hand has 6. This is what causes polarity. You could say that F has a bigger electron cloud around them than O which causes polarity.