Focus Problem 3F.1

[Talia Leano 2H]

How do you approach this problem?

[Tam Nguyen 2B]

They're asking you to just list what IMFs are present in each of the molecules. All of them will have London Dispersion of course. So the best way of identifying any other ones would be drawing their lewis structures because you'll be able to see how/which atoms are bonded together.

[SavannahScriven_1F]

I would first go through the rules of drawing lewis structures. From there, you have to identify which molecules are polar and which are nonpolar. Polar molecules would have dipole-dipole intermolecular forces. To tell if a molecular is polar, you should look to see if the molecule has different regions of electron density. This is apparent in NH2OH - there is a dipole moment between the O and H because O is so electronegative. There is also some between the N and H because N is pretty electronegative compared to H. This molecule is polar, so it would have dipole-dipole interactions (in addition to induced-dipole induced dipole interactions, which are always present). Next, look for the ability to hydrogen bond. Are there H atoms present? Is it bonded to N, O, or F? Does the O or N of a neighboring molecule of the same type have a lone pair available? This will help determine if hydrogen bonding is present.

[SavannahScriven_1F]

If you're having trouble identifying which molecules are polar and nonpolar, I wouldn't worry about it too much because we will learn this in greater detail as we dive more into the molecular shape :) Knowledge of the molecular shape really helps in determining if something is polar or not.

[AmyHo2K]

I usually start out by drawing the Lewis structure to see how everything is bonded then seeing what kind of interactions each atom has with another.

[Andrew Yoon 3L]

First, I would draw out the lewis structures for all of the compounds. You know all of them have LDP. Next, I would check for hydrogen bonding. That only happens between H and O, N, or F. Dipole-dipole interactions occur when a partially negative part apolar molecule is attracted to a partially positive part of a second polar molecule. Ion-dipole interaction occurs when either a partial positive or negative area of a polar molecule is attracted to it's oppositely charged ion.