Why isn't Yttrium considered a Rare Earth? Or can it be?

[Yossarian]

1. Ce-Lu form the inner transition series, each with 2-14 electrons in the 4f block.

2. La + Ce-Lu are collectively called the “Rare Earth Elements” because of their similarities, even though La doesn’t have f-electrons, instead having an outter-shell electron configuration of 5d1 6s2.

3. Y has the same outter shell configuration as La: 4d1 5s2.
   Additionally, it has the same size and charge as the HREE (esp. Ho) and “behaves” similarly in geochemical systems.

So, why isn’t Y generally considered to be a REE? Or is it? Or is it not, but can be?

[scm1001]

according to Cotton and Wilkinson “advanced inorganic chemistry” Yttrium can be considered a rare earth metal

[Polski_King]

Im pretty sure it is considered rare earth - er thats how i knew it anyhow

-PK

[Steve_Wright]

I’m not a chemist… but I’ve read Isaac Asimov’s essays on the discovery of the rare earth metals (in his collectionThe Stars In Their Courses), where he includes yttrium (and its neighbours scandium and lutetium) in the category.

I think there may be a distinction of terminology here, though; scandium, yttrium and lutetium may be rare earths, but they’re group 3 elements, not part of the lanthanoid transition series which includes all the other rare earths. So, there may be some tendency among chemists - heck, for all I know, it could be official nomenclature - to say “rare earth=lanthanoid”.

(Obligatory reference link to WebElements)

[Threadkiller]

Some Cites:
Chemicalelements.com does not list yttrium as a REE.

http://www.esu1.k12.ne.us/~lweb/Lakeview/science/y.htm:

Yttrium is considered a rare earth element and is often associated with them, even thouth Yttrium only has two electrons in its outer shell. The rare earth elements are the atomic numbers 58-71. They have three electrons in their outer shell. True rare earth elements are silver colored metals. In nature they are found with non-metallic elements.

http://www.iversonsoftware.com/reference/chemistry/r/Rare%20Earth%20Elements.htm

Rare Earth Elements, series of chemical elements of the periodic table
The rare earth elements (or rare earth metals) include the elements with atomic numbers 57 through 71, and, named in order, are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Yttrium (atomic no. 39) and scandium (atomic no. 21) are sometimes included in the group of rare earth elements.

http://www.pir.sa.gov.au/pages/minerals/resources/commodity/rare_earths.htm:sectID=245&tempID=7

Rare Earths
Rare earths were named by Johann Gadolin in 1974 for a group of chemically similar, metallic elements with atomic numbers 57 through to 71. In order, these are lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium ™, ytterbium (Yb) and lutetium (Lu). These elements are commonly known as the lanthanide series and are divided into light rare earths (lanthanum-gadolinium) and heavy rare earths (terbium-lutetium). Scandium (Sc, atomic number 21), yttrium (Y, atomic number 39) and thorium (Th, atomic number 90) are also generally included in the rare earth group because of their similar chemical properties. [italics mine]