What’s Up With Ammonium?

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Um, What’s Up With Ammonium?

Ammonium is a word that seems to be around in the world a great deal.  Practically every label we read on things ranging from food to cleaners has some kind, or even kinds, of ammonium in it.  But have we stopped and asked ourselves, what, exactly, is an ammonium?  With so much of it around us in the world, perhaps we should know a bit more about it.

In Simple Terms

Put in the simplest terms, ammonium is a kind of molecule called an ion.  The ammonium ion is relatively simple in that it contains only 5 atoms, four of which are hydrogen and one of which is nitrogen.  Both of those are colorless, tasteless, and odorless gases, so we might think that ammonium is as well, but the fact is that no one knows what ammonium looks, smells, or tastes like since you can’t ever have a jar, or any container for that matter, of ammonium.  What??  How can that be?  How can we know what something is made of but not know what it looks like?  While doubtfully a consolation, it is expected, due to some chemical and structural similarities, that at extremely great pressure, such as is achieved on the gas giant planets of Neptune and Uranus, that ammonium behaves, if perhaps doesn’t look like, an alkali metal such as lithium, sodium, or potassium.  But for a more Earthly explanation, let us back up a bit.

Electrical Charges

We noted that ammonium is an ion and to better understand what we can’t know about ammonium we have to know more about ions.  An ion is a molecule that carries an electric charge, either positive or negative, ranging from 1 to 7 in either direction.  For example, sodium ions almost always carry a plus 1 electric charge while chlorine atoms infamously range in possible charges from negative 1 to negative 7, and sometimes even carry positive charges.  Oxygen almost always carries a negative 2 charge.  The number isn’t what matters for our purposes here, although the number, or amount of electric charge, is critical in most all applications of chemistry.  What matters here is that a charge exists.  So, an ion is a molecule with an electric charge.

Ions are the state that a molecule is in when it combines with one or more other molecules to make a new molecule.  For example, in table salt, there are two ions, a positive sodium ion and a negative chlorine ion.  Regular, uncharged sodium is a soft, silvery metal and uncharged chlorine is a poisonous greenish-yellow gas.  But together, each in ion form, we know they form a white crystal solid.  So ions are very powerful and important things since without them we couldn’t have new molecules or compounds like table salt, which we need to live.

But as important as they are, ions, any charged molecule, can’t exist freely in nature as we know it.  They only exist when combined with one or more other ions to form an electrically neutral compound that we can see, taste (never do this with an unknown substance) or smell (ditto).  When something dissolves, like salt into water, we know that the ions are floating about in solution and that this ability to come apart is the reason some things dissolve in the first place, but we also know that once the water dries up, the ions will recombine into table salt crystals before we can see the ions.  So, you can never have a jar of any ion, any molecule that carries an electric charge, including the ammonium ion, and that is why we don’t know what it looks, tastes, or smells like.

Radioactive Ammonium?

It is possible that at this point someone might ask: “But what about radioactive molecules?  They create electricity so don’t they have an electric charge and exist freely in nature?”  That is a great question and the answer is that while radioactive elements can be used to create energy, they don’t themselves carry an electric charge and exist freely in nature.  Radioactive elements, like uranium, can be in the form of ions.  For example, in the gas uranium hexafluoride, which is the stuff that Iran gets in so much trouble for wanting to make and then place in giant centrifuges, uranium is an ion with a positive 6 charge, but uranium in this form, like any other ion, can’t exist freely in nature uncombined with other molecules.  Uncharged uranium is a shiny, albeit very heavy, metal.  You could hold a chunk of it in your hand, and yes you can do this safely provided the metal is not “enriched” or purified to concentrate the radioactivity, but as we now know, you can’t hold a chunk of uranium ion uncombined with something else.

Radioactive substances are used to create electricity because as part of a complicated decay, or breakdown, process the actual atoms inside the radioactive substances are coming apart and as they do so they release energy in the form of heat.  That heat is captured and used, most commonly, to heat water to create steam to turn giant steam turbines that create electricity.  If the heat is not controlled, it can, in very specific circumstances, become explosive.  This radioactive heat is what fuels volcanic phenomena on Earth.  There is so much radioactive material in the inside of the Earth that is remains very hot, but this heat is not even remotely the same thing as an electric charge on an ion like ammonium.

So, we know that ammonium is a charged molecule called an ion that can’t exist freely in nature; it only occurs when combined with something else.  In the case of ammonium, one of the things it is most commonly combined with is another ion, this one with a negative charge, so they attract each other and hold tight, called hydroxide, made of one oxygen and one hydrogen, and together they form ammonium hydroxide, or what is usually meant by the term “household ammonia” such as we talked about in a previous post.  Ammonium hydroxide is made by dissolving ammonia gas in water.  This makes, among other uses, a product commonly used as a cleaner.  It works as a cleaner because the solution is alkali, or basic as opposed to acidic, and bases work great as cleaners because they have the ability to break down organic molecules such as fats and other animal and plant based stains.

Looks like, but isn’t

However, there are many other molecules that contain the ammonium ion and many of these do have a relationship to the ammonia gas we talked about before.  But be careful in making too many assumptions based on names because chemistry can be tricky to the uninitiated.  Sometimes a substance might be called “ammonium something” just because it chemically resembles ammonia or the ammonium ion even if has no relationship at all to ammonia or ammonium as we have talked about it here.  One great example of the name ammonium meaning “looks like” instead of “has a relationship to” is the term “quaternary ammonium compounds,” or quats, the substances that make cleaners such as MoldStat work.  We will talk about this more in another post to come, but in the meantime think of it this way: we all know Plexiglas isn’t glass, but we call it that anyway because it looks like glass!

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