Friday, April 11, 2014

Element of the Month: Lead!

April's Element of the Month:


Atomic Mass: 207.2
Melting Point: 327.46 °C
Boiling Point: 1749 °C

I had two main questions about lead. The first was this: we've seen lots of elements now that are very hard to isolate because they don't appear in any concentration in nature. Why is it that other elements do appear in concentrated, or even pure, forms? Part of it must have to do with a certain level of resistance to chemical reactions with air and water, but what else is going on? Why might we, for instance, find here and there about the planet's surface extensive seams of galena, the mineral form of lead sulfide? After wandering around the various informational resources of the internet for a while, I've come to this conclusion: I don't really know. Geology was never my strong suit.

My other question was, "Why 'Pb'?" The answer there is that the Latin word for lead was plumbum.

As the heaviest non-radioactive element, Lead has always been popular when something heavy is wanted. It is also soft and maleable and has a very low melting point, which means it can be shaped easily. The Romans used it a lot, famously for their plumbing and less famously as a sort of soldering for iron in construction. They mined around 80 thousand metric tons of Lead a year, the Romans did, partly because it was useful in its own right and partly because it often hangs out with desireably shiny element Silver in nature. The Romans didn't think Lead was especially elemental, incidentally, and actually thought Lead and Tin were two different versions of the same basic thing.

The Centerfold!

A chunk of natural raw lead that somebody dug up somewhere!

After the collapse of Rome, lead production did like everything else and went into a steep decline, shrinking to virtually nothing before charging back to its previous level in the eighteenth century. We modern folks have the Romans beat 100-fold, although there are concerns that the world's supply could run out in, say, twenty to fifty years. However, since Lead is eminently recycleable and often used in applications where more common stuff would do just as well, it is probably not the most critical materials crisis you could be fretting over.

You probably know that lead used to be used in a carefree fashion in housepaints and as a gasoline additive, which exposed a couple of generations to a nasty level of environmental contamination. There's a lot less lead around to be casually inhaled and ingested these days, and this is universally held to be a good thing.  There is also a school of thought holding that environmental lead toxicity was the source of pretty much all the social ills of the the 1970s and 1980s. It's a bit silly, of course, but then most big theories are somewhat daft in their pure forms. Maybe there's a little something to this one.


gl. said...

gosh, that's the nicest centerfold of lead i think i've ever seen! who knew it could be so pretty?

Michael5000 said...

It looks a bit like two Klimptian lead lovers, entwined and staring into one another's eyes. Perhaps.