- #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
- Thread starter mickeyw
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In summary, the lanthanides and actinides are not necessarily broken off from the periodic table, as there are alternative forms that group them differently. However, they are usually grouped together based on similarities in chemical properties. This is because the lanthanides tend to form 3+ valences and have similar atomic radii. The transitional metals fall between alkali Earth's and poor metals and metalloids. The lanthanides and actinides could be placed between groups 2 and 13, but this would make the table too wide. The reason for the last electron of lanthanum and actinum entering the d orbital instead of the f orbital is due to energy levels. The 5d1 level is at
- #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 ?
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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.
1. What are lanthanides and actinides?
Lanthanides and actinides are two groups of elements that are located at the bottom of the periodic table. They are also known as the "inner transition metals" and are characterized by their similar electronic configurations and chemical properties.
2. How many elements are in the lanthanide and actinide series?
There are a total of 15 elements in the lanthanide series and 15 elements in the actinide series. These elements are also known as the "rare earth elements" due to their scarcity and difficulty in separating them from each other.
3. What are the properties of lanthanides and actinides?
Lanthanides and actinides have similar properties due to their electronic configurations. They are typically soft, silvery-white metals that are highly reactive and have high melting and boiling points. They also have a tendency to form colorful compounds and exhibit magnetic properties.
4. What are some uses of lanthanides and actinides?
Lanthanides and actinides have a variety of uses in different industries. Some common uses include as catalysts in chemical reactions, in the production of electronic devices such as computer screens and smartphones, and in medical imaging and treatment.
5. Are lanthanides and actinides radioactive?
Most actinides are radioactive, while only some of the lanthanides are radioactive. Lanthanum, cerium, and praseodymium are the only lanthanides that do not have any radioactive isotopes. The actinides are all radioactive due to their large atomic nuclei, which makes them unstable and prone to decay.
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