Weekly Blog 9/28 through 10/3

We began this week focusing on metallic bonding. We learned that in metallic bonding, there is essentially a cluster of cations with a "sea of electrons" flying around the cations, not associate with any particular atom. Also, alloys are made in two different ways: interstitial or substitial. Interstitial is when smaller atoms fill the space in between larger atoms, making the alloy more dense, and substitutional alloys are where two similarly sized atoms are mixed, which does not increase density. Here, substitutional is on the left and interstitial is on the right.

Alloys are essentially solutions of metals.

We also learned about the intermolecular forces, or IMF's, that exist such as hydrogen bonding, dipole dipole bonding, and LDF's, or London Dispersion Forces. These are all van der Waals forces. Ion-dipole bonding can also happen, but this is not a van der Waal force. Ion-dipole forces are the strongest, then hydrogen bonding, then dipole-dipole, then the LDF's (induced dipole-dipole and induced dipole-induced dipole). We learned that LDF's are present in all molecules, polar, non-polar, ionic, everything. They are, however, very weak and don't compare much to hydrogen bonding and ion-dipole bonding. Here is a good site about LDF's.

Another thing we learned was about the hydration spheres of ions in a solution, We saw that if you dissolve K+Cl- in water, the K and Cl will separate and get surrounded by water molecules. The water molecules will align themselves so that the positive end is towards the negative ion and the negative end is towards the positive ion. The sphere will also include hydrogen bonding because of the two hydrogens in water bonded to the oxygen.

I think I have a good understanding of the ideas we covered this week. I'm looking forward to seeing what role entropy plays in these molecules and also learning more about what entropy really is. I've heard of it before, but I get the impression that I don't know anything significant about it.