Lanthanum, #57

This metallic element gives its name to a whole series of similar substances—the lanthanoids or rare-earths. That name is a bit of a misnomer as lanthanum is three times more abundant than lead in the earth’s crust. The lanthanoids are noted for their many similar chemical properties and thus were not isolated and identified until the 19th and 20th centuries.

Most periodic tables show the lanthanoids below the main body of elements. This is due to the tyranny of 8-1/2 by 11 inch paper. They had to squeeze the damn table into a chart that would fit in a chem student’s binder! Here’s what I mean:

The lanthanoids are the numbers 57-71, La through Lu (Lutetium). It’s the brownish row, the top one of the bottom two. Lanthanum ought to fall in column 3, nestled between Barium (Ba, #56) and Hafnium (Hf, #72) and underneath Yttrium (Y, #39) and Scandium (Sc, #21). In fact both Y and Sc are often included with the rare-earths because of their similarity to La and the other lanthanoids. You can see the arrow from that empty spot in column 3 where they plucked out La and pasted it to the end of a the new row (Ce-Lu).

But the periodic table really ought to look like this:

You can see that this form would be a pain-in-the-ass. In the old days we would have folded the thing to make it fit. Nowadays you can just turn your phone sideways, I suppose. It’s not that important, mostly a matter of aesthetics. The lanthanoids are “f-block” elements (they fill the 4f electron shell) and this wide chart illustrates that a little better. Note the row below the lanthanoids: these are the actinoids and they are also f-block (they fill the 5f shell).

Lanthanum is used in alloys, particularly nickel-metal hydride (NiMH) batteries. It’s also used to make specialized types of glass. Interest in all the lanthanoids has exploded in recent years due to their usefulness in a wide variety of high-tech applications. Rare-earth mining has been in the news because the current world supply is dominated by China. There is a push to develop domestic mines and ore processing plants to meet the country’s growing needs and reduce reliance on a sketchy foreign power.

Mountain Pass Mine in the Mojave Desert is the largest known US deposit of rare-earth ore. There is also a new rare-earth mining venture in Texas called Round Top which aims to produce lithium as well. If it can’t be farmed, it has to be mined. There is no “green” future without some big holes in the ground!

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