Definitions:

Rare Earths

La-Lu and Y & Sc occur together in minerals ~ hard to separate from each other

{Th which occurs in many rare earth minerals is sometimes included in the definition}

Lanthanides

Usually taken to indicate the 15 elements from La-Lu or the 14 from Ce-Lu

Actinides

The 15 elements from Ac-Lw or the 14 from Th-Lw

Mnemonics:

Lanthanides

Actinides

Some Viewpoints

"Lanthanum has only one important oxidation state in aqueous solution, the +3 state. With few exceptions, this tells the whole boring story about the other 14 Lanthanides"

G.C. Pimentel & R.D. Sprately,

"Understanding Chemistry",

Holden-Day, 1971, p. 862

"These elements (rare earths) perplex us in our researches, baffle us in our speculations and haunt us in our dreams. They stretch like an unknown sea before us - mocking, mystifying and murmuring strange revelations and possibilities"

Sir William Crookes
Address to the British Association, 1887

Bibliography