Monday, July 22, 2013

Element of the Month: Iron!

July's Element of the Month:
The Eiffel Tower, one of the last structures built primarily from Iron. Also,
probably the largest.
George Seurat, 1859-1891. Anticipated Tournament debut early 2016.


Atomic Mass: 55.845 amu
Melting Point: 1538 °C
Boiling Point: 2862 °C

Iron, Element #26, is the sixth most common element in the universe. It's a good 5% of the admittedly marginal 2% of all matter that isn't Hydrogen and Helium.  You might be saying to yourself "But why? How did such a relatively large, complex element get to be so darn relatively common?"

Well, it's an excellent question, even though you used the word "relatively" twice in the same sentence.

You probably have something between a vague sense and a solid understanding that "the sun is a mass of incandescent [plasma], an enormous nuclear furnace where Hydrogen is burned into Helium at a temperature of millions of degrees." If you are like me, you probably visualize this as a zillion atomic bombs going off simultaneously all the time; however, I read recently that the production of energy per cubic meter in the sun is roughly equivalent to that of a really good compost pile. However, the sun is really, really, really big, and all of that energy really adds up. The outward pressure from the furnace overcomes the force of gravity, the sun retains its volume and density, and we here on earth bask in the sunshine.

But eventually, any given star is going to run out of hydrogen. What happens then is that the furnace stops producing energy and outward pressure.  Gravity starts to compact its mass, which is now mostly Helium. As the star compacts in on itself, the density eventually becomes so great that fusion kicks in again, and for a while the sun will be "an enormous nuclear furnace where Helium is burned into Carbon and Oxygen at a temperature of millions of degrees." Carbon and Oxygen, incidently, are the fourth and third most common elements in the universe.

After that, it kind of varies depending on the size of the star. If it's a big 'un, Carbon and Oxygen can fuse into Neon, Sodium, Magnesium, Sulfur and Silicon. From there, in one last spasm, a really big star -- now a small but incredibly dense star -- can for a brief time fuse these elements into Calcium, Iron, Nickel, Chromium, and Copper -- with Iron, as you may have guessed, being a major player. And since it's the biggest stars that generate Iron in their end-game, naturally they generate a lot of Iron. (They also pump out 56Ni, a radioactive isotope of Nickel that decays into Iron in a few weeks.) So that's why there's so much Iron in the universe, and in general why the common elements are common.

Now then.  Closer to home, Iron is the MOST common Element on the planet Earth. Now, before you go all "nuh uh!" remember that your daily experience occurs entirely on and above the CRUST of the Earth, which is not representative of the whole. Dig down deep enough (this will take special equipment) and you will eventually get to a point where it's almost ALL iron. Oxygen takes a close second to Iron in the Earth's composition, and is very prevalent in the crust, where pretty much every rock or mineral you've ever seen is some kind of oxide. Everything other than Iron and Oxygen put together only makes up about 1/3 of the Earth. So yes, essentially you live on a great big rustball.

The Centerfold!

Iron was discovered by Joseph Priestly in... no, no, I jest. Iron has been known and worked since at least Biblical times. You've heard of the Iron Age. It came after the Bronze Age in theory, although in reality it took Iron many, many centuries to surpass Bronze in human use. Iron is tricky to get right, and unless you really know what you are doing it you will make it too soft or too brittle to be much use. Also, there's the rust issue. In most metals, a patina of oxide will protect the interior of the metal, but iron expands when it oxidizes, which means that rust flakes off and exposes the interior to more corrosion. For those of us born well on in the Industrial Revolution, Iron is mostly the main ingredient of steel, which was also known in antiquity but didn't really hit its stride until Henry Bessemer came up with the "Bessemer Process" for cheap, efficient steel production in 1858.

I have read it speculated that if we humans ever let our tech level slip too far again (like after the Fall of Rome, say), that we would be permanently screwed, because all of the easily mined sources of Iron are tapped out, and there would be no way to produce the Iron and steel needed for the major tech revolutions. That's not true, though -- Iron would actually be very easy to mine and scavenge from among the ruins. It's easily mined sources of ENERGY that would git us, as we've made quite a dent in the more accessible layers of coal. Just another reason to do your part to keep our human civilization kicking sustainably along, if you needed one.


Elizabeth said...

I approve of the fusion of art and science.

Michael5000 said...

Aw, you noticed!

gl. said...

scientists have found that the sun is a huge atom-smashing machine!

Michael5000 said...

You know, I've heard that!