Question

Identify type of interactions force bonding between following molecules.

HHHN -----HNHH

H---O---H

Na----Cl

Na-----OHH

Au----Au

HCl-----HCl

HH----HH

Answer 1

let's review the kinds of intermolecular forces you can have:

1. dipole-dipole - this when different atoms in the same compound have electronegativities that are pretty different, causing a permanent shift in how the electrons are distributed (i.e. they will surround the more electronegative atom in the bond). For instance, the C-H bond is pretty much nonpolar because both C and H have about equal electronegativites. However, the C-O bond is polar, and any molecule containing a C-O bond will have a dipole between those two atoms.

2. London/dispersion/van der Waals forces - these are weak interactions that occur in a matter of nanoseconds when one atom in a bond temporarily takes more of the electron density than the other one, causing a temporary dipole - i.e. this can happen even when you have a C-H bond that is normally nonpolar.

3. hydrogen bonding - these are interactions between hydrogen of one molecule and O, F, or N with a lone pair on a second molecule (or two atoms on a large molecule...). This is what holds DNA strands and helices together!

HHHN -----HNHH: van der Waals, dipole, and hydrogen bonding (using the lone pair on each nitrogen as acceptors) with another molecule that has a donor H.

H---O---H: hydrogen bonding.

Na----Cl: Intermolecular - within a molecule - interactions between atoms or ions in a particular molecule. Ionic

Na-----OHH: van der Waals, dipole, and hydrogen bonding

Au----Au: ionic

HCl-----HCl: Dipole-Dipole

HH----HH: covalent