Occurrence and separation of the lanthanoids

The spectroscopic and magnetic properties of actinoids are complicated and we mention them only briefly. Absorptions due to 5f 5f transitions are weak, but they are somewhat broader and more intense (and considerably more dependent 

All the lanthanoids except Pm occur naturally. The most stable isotope of promethium, Pm (P-emitter, h = 2.6 yr) is formed as a product of the fission of heavy nuclei and is obtained in mg amounts from products of nuclear reactors. 

A typical cation-exchange resin is sulfonated polystyrene or its Na+ salt. When a solution containing Ln + ions is poured on to a resin column, the cations exchange with the or Na ions (equation 25.2). 

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