LANTHANIDES

Abundance & Distribution

• Not especially Rare!

except Prometheum (¹⁴⁷Pm, t_1/2 = 2.6 years) which is produced artificially

e.g. La, Ce & Nd are more common than Pb

"Rare Earth" label not really justified today

• Most-common minerals:

monazite & xenotime (mixed La, Th, Ln phosphates)

widely-distributed, concentrated in sand & river beds due to relative insolubility

bastnaesite (a La, Ln fluorocarbonate M^IIICO₃F)

a vast deposit in Sierra Nevada, USA ~ discovered in 1949 ~ supplies much of world's needs

60-70% of the metal content of these minerals is rare earth oxide

• Elemental Proportions of Rare Earth-Content of Minerals

• Abundance of lanthanides in nature

• abundance shows even-odd alternation with atomic number
• mirrored by several/few alternation of number of stable isotopes with even/odd Z

 

• Due to nuclear shell structure (see : P.A. Cox, The Elements, OUP, 1989, p. 17, 36-44)