Scandium - the most obscure of transition metals

 Scandium - the most obscure of transition metals

Scandium (Sc), with the low atomic number 21 is the lightest of all transition metals on the periodic table - both in the atomic mass and the density. Scandium's density of barely 3 grams per square centimeter makes it different from any of it's neighbors. It is however similiar in many chemical properties to it's cousins from the lanthanides row and together with them and yttrium (Y), they create so called rare earth elements group.

Dendritic scandium metal.

Scandium metal is not something that most people can come across in a daily life. My sample of just 1 gram of distilled scandium dendrites can be bought anywhere from 15 to 25 dollars, depending on the seller and due to the steep price, it's sometimes offered even in 0,1g quantities for less demanding collectors (which is somehow acceptable, as the metal's low density causes even light samples to be noticeable).

 

Scandium, just like most other rare earth metals, is not necessarily rare on Earth, but due to it's complicated recovery from the ores, the prices skyrockets, similarly to thulium (Tm) or lutetium (Lu).

Metallic Sc is really unique in it's pure form and the photos don't really do it justice. It combines a subtle metallic shine, partially suppressed by the passive oxide layer, and a beautiful olive green hue, different from any other metal. The color of scandium metal is something in between ytterbium's (Yb) brassy gold and germanium's (Ge) greenish shine.

Other elements where this unlikely color can be observed in the elemental forms are praseodymium (Pr), which oxidizes into a dusty green oxide and europium (Eu), which when heavily oxidized is very reminiscent of moss.

Scandium's existence was actually predicted by Mendeleev, who knew about the empty space where a nucleus of a certain mass should be. He called it eka-boron, which might sound surprising, when you look at the periodic table.

Pure scandium metal has basically no uses, apart for making a nice sample. Alloyed with aluminum it's an important component of precipitation-hardened alloys, used in sports and aerospace industry (and a couple of bizzare firearms). In the form of compounds it is used in lighting, for an example metal halide lamps, where an iodide is utilized or in specialized ceramic parts, where an oxide (also called scandia, similarly to silica, zirconia or yttria) is pressed into a shape and sintered.