Bond. Chemical Bond.

Might as well ride this puppy all the way to the end (of the week).

In chemistry, there are several ways that atoms can connect with each other to form molecules.

If two atoms each have one electron available (one that is not tightly bound to the nucleus) and one space empty which an electron can fill, a covalent bond can be formed.  In this bond, the atoms share their available electrons, so that each atom can be considered filled.  A simple example is the H₂ molecule. Each hydrogen atom has one electron, and can be filled when it reaches two (if you don't know why, don't ask; it gets complicated quickly). So by sharing electrons, each atom becomes stabler.

If, on the other hand, you have one atom with one more electron than it needs for a full set (say, for example, sodium) and one atom that is one electron short of a full set* (e.g. chlorine), the first atom can actually "give" the electron to the second, forming an ionic bond.

In a more complicated system, you might (for example) have a large number of atoms of a metal, many of which tend to be short one or more electrons.  When those atoms arrange themselves into a large structure (a block of metal as opposed to a single atom), the electrons have a tendency to un-attach themselves from their original atom and go wandering around, re-attaching themselves sporadically to other atoms.  Imagine a big parking garage, with cars pulling into and out of different parking spots but never actually leaving.  The forces that keep pulling the electrons temporarily down into different nuclei are what hold the whole megillah together.  This is called a metallic bond.

There are more bonds, of course, but they get progressively more complicated and obscure.  These are the ones you're most likely to encounter in Chem 101.

*"He's one electron short of a full orbital" is a favored insult in a certain circle of especially geeky chemists†.

†That circle being the one that exists in my head.

Bingham Plastic Fluid

You may be familiar with the popular material science concept of the "non-Newtonian fluid," also known as the "walking on custard" trick.  This is a substance whose viscosity is variable, and (for the most part) will increase proportionately to the impact of another substance on it.  In other words, the harder you hit it, the stiffer it gets.  Jump up and down on it, and it's practically a solid-- stand still, and you start to sink in.

A similar class of substances is the Bingham Plastic, named after chemist Eugene Bingham, who was a rheological pioneer.  It is similar in that its physical properties vary depending on the applied stress, but it actually acts in the opposite fashion-- under no or low stress, it acts like a solid, but if you apply stress to it, it begins to flow like a liquid.  A good example is a stiff mayonnaise-- it spreads smoothly under pressure, but left alone it retains the peaks and ridges left by the knife.

The Good, the Bad, and the Nitrogen

As a professional science-y word type person (hey, I'm off the clock), I was somewhat familiar with the Haber-Bosch process.  But I knew nothing about Fritz Haber himself, until Radiolab did a segment about him.  And I have to say, I learned a lot-- rather more than I was expecting, in fact.

First some background.  Nitrogen is a really really useful thing.  It's one of the most important elements that compose complex organic structures, such as amino acids-- the things that make up DNA.  So when you dump materials rich in nitrogen onto plants, for example, they tend to grow really well.  In addition, atoms of nitrogen tend to bond very strongly to other atoms, holding on to a lot of energy in the process.  When you break those bonds, you get all of that energy at once.  Boom.  So there has historically been a lot of interest in finding a way to produce nitrogen in a form that can be manipulated.  

Those tight bonds kept it wrapped up, though, until in the very early part of the 20th Century Fritz Haber developed a process (mix this with that under these conditions in the presence of something else-- it's not really all that interesting in itself, so I'll skip the details) for producing reliable quantities of ammonia, which contains nitrogen and also can be much more easily combined with other things to make different products.  He sold the process, and together with Carl Bosch scaled it up to produce massive amounts of fertilizer for Germany.  Hooray!  Food for the Germans!  Spaetzle for everyone!

A good thing, right?  Nitrogen fertilizers have massively increased the amount of food that can be grown on a given plot of land.  Ok, so there are some environmental consequences that they didn't foresee, but I have to admit I still think that we're better off.  Massive starvation is bad, m'kay?  So he's a hero!  Nobel Prize for Haber!

And then came The Great War.  Suddenly, Germany had another use for the nitrogen-- weaponry.  Explosives.  So, ok, not the happiest thing in the world, but he was honored to serve his country, and that's the way it goes sometimes.  But he didn't stop there.  He had the brilliant idea of using the large quantities of ammonia to produce weaponized chlorine gas (despite its use being outlawed by treaty).  So, all right, maybe he's getting a little too intense, here.  But then he goes himself to the front lines, and personally supervises the release of large quantities of chlorine gas into British trenches.  Hooray!  Death to the enemies of Germany!  Horrible, wretched death!

So, he's still a hero, at least in the eyes of the German military.  But he's kind of starting to creep everybody else out.  In fact, his first wife ends up committing suicide, presumably (although never explicitly proven) as a response to his work.  His reaction?  He ships out that day to the Russian front to gas more enemy soldiers.

I don't know if this is a good guy or not.  Ultimately, his work has probably helped a lot more lives than it's harmed.  But it's hard to get a read on his intentions.  Did he want to be a hero?  Did he want to save the world?  Was he cold and unfeeling?  Bloodthirsty?  I just don't know.  All I can think is that maybe he should have spent just a little bit more time considering the consequences.

Al(OH)3

Alumina trihydrate (or ATH) is one of the most common commercial flame-retardant compounds on the market.  When heated to about 350 degrees F, Al(OH)₃ decomposes into Al₂OH₃·3H₂O, absorbing a lot of heat energy and releasing water vapor.  Both of these processes naturally tend to slow the generation and spread of flames.

I have to admit, I don't really find this very interesting, but I spent 2-3 hours today wrestling with the distinctions between alumina trihydrate, aluminum hydrate, and aluminum hydroxide (all of which are basically different names for the same thing in different contexts), and by the time I was done I had definitely learned something.