similarities and dirrerences with rare earth metals ?

Question

can you list 4 similarities and 4 differences in rare earth metals ?

thanks :]]

Answer 1

Check out this paper: Rare Earth Metals Find Interesting New Uses Despite Lack of Engineering Data.

By Roman Lundin and John R. Wilson

at http://www.arrisintl.com/customer/Papers/remetalspaper.html

here's an excerpt:

The rare earth elements or lanthanides consist of fourteen elements plus lanthanum. For practical reasons, the list often includes scandium and yttrium for a total of 17, since these two elements are very similar in characteristics to the lanthanides. For ease of discussion and also for convenience in assessing their potential processability and use, the rare earths are best classified into five unofficial 'groups':

Group 1 lanthanides have low melting points and high boiling points - lanthanum, cerium, praseodymium, neodymium.

Group 2 lanthanides have high melting points and high boiling points - gadolinium, terbium, yttrium, lutetium.

Group 3 lanthanides have high melting points, mid to low boiling points and a high vapor pressure at the melting point - dysprosium, holmium, erbium and scandium.

Group 4 lanthanides have low boiling points - samarium, europium, ytterbium and thulium.

Group 5 lanthanides - this group contains just one element, promethium, which really belongs in Group 1 but is highly radioactive and for that reason has no significant commercial uses.

The grouping of the lanthanides in this way also correlates with their processing characteristics. For example, the group 3 lanthanides are difficult to handle in vacuum-remelting equipment because of their high vapor pressures - they are better refined by a sublimation method. The group 2 and group 3 lanthanides are difficult to contain in metal or ceramic crucibles as liquids at high temperature because of their high melting points. The group 1 lanthanides offer some of the broadest liquid ranges (LR = BP-MP) of any of the elements. Note that the group 4 lanthanides do not have unusually high vapor pressures close to the melting point despite their relatively low boiling temperatures.

Despite the differences that permit this classification, the rare earths are chemically more similar than different, a characteristic that has presented major difficulties in their separation and purification.