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Question about lanthanides and actinides

  1. Sep 20, 2005 #1
    I have a question about lanthanides and actinides.... is there any reason that they broke both the lanthanides and actinides from the periodic table?
     
  2. jcsd
  3. Sep 20, 2005 #2

    Astronuc

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    That is not necessarily the case. This website - chemlab.pc.maricopa.edu/periodic/periodic.html - has alternative forms of the periodic table, however there seems to be some problem with it at the time this is posted. But the main idea is that there are alternate forms that do not 'break out' the lathanides and actinides. They are grouped however for reasons of similarity in some chemical properties. For example, the lanthanides tend to form 3+ valences, and so the oxides are generally M2O3. The atomic radii are fairly close for the lanthanides and actinides - http://www.webelements.com/webelements/properties/text/image-balls/atomic-radius-emp.html

    The transitional metals fall nicely between alkali earths and poor metals and metalloids - see http://en.wikipedia.org/wiki/Periodic_table for an explanation.

    See also http://www.webelements.com/.

    One could put the lanthanides and actinides (periods 6 and 7, respectivley) between groups 2 and 13, but then the table would be very wide. See - http://en.wikipedia.org/wiki/Periodic_table_(wide)
     
    Last edited: Sep 20, 2005
  4. Sep 20, 2005 #3
    They broke them off just so that the periodic table would look nicer. If they we all together they would have to be in the middle of two other rows (as opposed to having two rows of their own) and thus the periodic table would be impracticably long and hard to print.
     
  5. Sep 21, 2005 #4
    y thanx! :biggrin:
     
  6. Apr 27, 2007 #5
    why the last electron of the element lanthanum enters the d orbital instead of entering the f orbital ?Same in actinum ? Why ??????????????
     
  7. Apr 29, 2007 #6

    Astronuc

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    http://www.webelements.com/webelements/elements/text/La/econ.html
    There is a really cool flash (9) player for electron configs. One can browse by Z.

    Ostensibly the 5d1 level is at a lower energy state than 4f1. Cerium (Z=58) then has 5d14f1, but praseodymium (Z=59) has 4f3.

    Then Gd (Z=64) has electronic config [Xe].4f7.5d1.6s2, and all the 4f electrons are unpaired. Gd has some interesting magnetic properties.
     
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