How to tell polar and nonpolar?

Question

I was wondering how you can tell the difference between polar and nonpolar molecules by looking at the molecular formula....
so i guess im asking, by looking at a molecular formula how can you tell whether the substance is polar..then nonpolar...and i need to list 4 categories with some examples..please help me out:)

Answer 1

A non-polar molecule is one that the electrons are distributed more symmetrically and thus does not have an abundance of charges at the opposite sides. The charges all cancel out each other.

If you take CO2 as an example, the electrical charges in non-polar Carbon Dioxide are evenly distributed.

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Chemical bonding is the result of either an atom sharing one or more outer orbit electrons with another atom or an atom taking outer orbit electrons from the atom with which it is bonding. Normally, an atom has an even distribution of electrons in the orbits or shells, but if more end up on one side that the other in a molecule, there can be a resulting electrical field in that area.



Water is a polar molecule because of the way the atoms bind in the molecule such that there are excess electrons on the Oxygen side and a lack or excess of positive charges on the Hydrogen side of the molecule. In short, water is a polar molecule with positive charges on one side and negative on the other.

Answer 2

First, unless a molecule has polar covalent bonds, it can never be a polar molecule. In molecules like H2 and O2 the bond is not polar, so the molecules are not polar either.

So, you have to think about the electronegativities of the bonded atoms and start there. No polar bonds, nonpolar molecule. However, if there are polar bond, the molecule might still be nonpolar. (For example, CCl4). The only way to determine whether a molecule is polar or not is to think about the actually shape and geometry of the molecule. You can get a good idea by drawing a Lewis structure for the molecule and then move from that to the actual 3-dimensional structure. You can think about the polar bonds pulling or pushing on the central atom. If the forces are all symmetrical and balanced, the molecule will be nonpolar. If they aren't, then the molecule is polar.

Hope this helps some. I'm not sure what you're after with "4 categories with some examples.

Answer 3

You need the structural formula to tell whether the molecule is polar or nonpolar. In covalent compounds, elements with higher electronegativity (those more toward the right of the periodic table and toward the top) tend to acquire slight negative charges. Those of lower electronegativity, slight positive charges.

For example, water is polar, partly because O has lower electronegativity than H, so there is a separation of + & -. But also, water is not symmetrical, H-O-H, but shaped like a boomerang, H^H, so the head of the boomerang is a little (-) and the two tails are a little (+)

Carbon dioxide is linear and so symmetrical, O=C=O. So although the O's are (-) and the C is (+), the two dipoles pull in opposite directions, and the molecule is overall nonpolar

Answer 4

the polar bonds are arranged asymmetrically around the crucial atom in an inclination shape as there are 2 lone pair of electrons on the crucial atom. The bond dipoles do not cancel and the molecule is polar. for that reason cocl2 is polar.

Answer 5

Basically, if the electrons are more often present on one particular side of the molecule, it is polar. You have to look at electron affinity and calculate it out. I forgot how to, but I remember it was a little complicated..takes like 15 minutes to learn with the right resources in front of you., Nitrogen and oxygen tend to take electrons for themselves. I hope this helps you with some pointers about where to start looking for resources. You can look here to start:
http://en.wikipedia.org/wiki/Nonpolar

You got to draw out the double bonds and chains and label it as I remember.