- #1
mickeyw
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I have a question about lanthanides and actinides... is there any reason that they broke both the lanthanides and actinides from the periodic table?
Question about lanthanides and actinides
- Context: Undergrad
- Thread starter mickeyw
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Discussion Overview
The discussion revolves around the placement of lanthanides and actinides in the periodic table, exploring reasons for their separation from the main body of the table and addressing questions about their electronic configurations.
Discussion Character
- Debate/contested
- Conceptual clarification
- Technical explanation
Main Points Raised
- Some participants suggest that lanthanides and actinides are separated in the periodic table primarily for aesthetic reasons, as grouping them together would make the table impractically long.
- Others argue that there are alternative forms of the periodic table that do not separate these elements, citing similarities in chemical properties as a reason for their grouping.
- A participant raises a question about why the last electron of lanthanum enters the d orbital instead of the f orbital, suggesting a similar situation for actinium.
- Another participant provides information about the electronic configurations of lanthanum and cerium, noting that the 5d level is at a lower energy state than the 4f level for lanthanum.
- Discussion includes references to external resources for further exploration of periodic table formats and electron configurations.
Areas of Agreement / Disagreement
Participants express differing views on the reasons for the separation of lanthanides and actinides in the periodic table, with no consensus reached on the matter. Additionally, there is an unresolved question regarding the electronic configurations of these elements.
Contextual Notes
Some claims about the electronic configurations and energy levels are presented without consensus on their implications or correctness. The discussion also references external resources that may not be accessible to all participants.
- #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.htmlmickeyw said:
The transitional metals fall nicely between alkali Earth's 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_%28wide%29
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- #3
Tzar
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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.
- #4
mickeyw
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y thanx! 
- #5
madhusudan
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why the last electron of the element lanthanum enters the d orbital instead of entering the f orbital ?Same in actinum ? Why ?
- #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.
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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