If you look at the periodic table, can you identify the elements known as lanthanides? Don’t worry if you can’t — they’re not a type of element you’re likely to encounter on your daily walk through the park. Also known as rare earth elements, these 14 elements all fall between the atomic numbers of 57 and 71 and have their own section on the bottom of the periodic table. What are lanthanides and where might you encounter them in your everyday life?
What Will Scientists Discover Next?
Science news delivered weekly!
First, let’s take a look at the elements that make up the lanthanide group. In spite of the group’s nickname, rare earth elements, these elements aren’t all that rare. These include:
The only exception to this abundance is promethium, because it is produced artificially in the lab.
Occasionally, scandium and yttrium are included in this group, but we’ve already discussed these in a previous piece, so we’re going to leave those two out of this discussion.
Chemical and Physical Traits of Lanthanides
While lanthanides are fairly common in the Earth’s crust, they tend to be very difficult to extract in usable quantities. These elements are bright and usually silvery — at least until they are exposed to oxygen. They are highly reactive, and while they’re not explosive, they tarnish quickly — which also makes them susceptible to contamination from other elements.
Not all lanthanides tarnish at the same rate. Lutetium and gadolinium, for example, can be exposed to air for long periods without tarnishing, while elements like lanthanum, neodymium and europium are highly reactive and must be stored in mineral oil to prevent tarnishing.
All members of the lanthanides group are extremely soft. Most can be easily cut with a knife and don’t require any heavy-duty tools to remove them from the earth.
These elements aren’t considered rare because they’re hard to find. They’re rare because it is difficult to extract sufficient quantities of the pure form of each element to meet any and all industrial needs.
Where can you encounter these rare earth elements in your daily life, other than in a lab?
You might have cerium in your pocket. Named for the planetoid Ceres, which orbits in the asteroid belt, this element is used in lighters because it sparks when rubbed against metal. It’s also found in jet engines and fuel additives because it’s a fairly effective anti-knock agent in gasoline tanks.
Gadolinium is always found with yttrium, and while it could potentially be used in nuclear reactors for capturing neutrons, there isn’t enough of it to make it useful in this application. It’s primarily used as a phosphor in television sets — though some research has shown that at low temperatures, it could be used as a superconductor as well.
If you wear or use specialized lenses, you may have encountered lanthanum, which is used in the manufacture of glass lenses for a variety of applications. When you mix it with oxygen or fluorine, it can also be used to create carbon-arc lamps — but these are primarily used by Hollywood.
Samarium shares a lot of applications with lanthanum — optical lenses, laser and arc lamps. It is also used to create electromagnets when alloyed with cobalt.
You can’t make pink without erbium, at least if you’re using it to tint glass or porcelain. Terbium, on the other hand, is brilliantly green when exposed to electrons, which means it is perfect for television phosphors.
The rest of the elements in this group have little to no practical application. They’re either too reactive, too expensive to mine or simply have no industrial use. You may find them in televisions as phosphors, in nuclear reactors or even in postage stamps — europium allows them to be scanned electronically. They’re certainly not the kind of element you’ll see in your local grocery or department store.
Have you spotted any lanthanides in your everyday life? Let us know! If you’ve got any questions about these rare earth elements, feel free to reach out. We’d love to hear from you! What is your favorite element from the lanthanide group?