Talk:Lanthanide contraction

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All this are the consequenzes of the Lanthanide contraction not the Lanthanide contraction. I always thougt the Lanthanide contraction is that the Lanthanides decrease their ion radii while more and more electrons are added in the periodic table. This happens due to the fact that the electrons are added to a relative low shell and the increasing number of protons atract the new electrons. The effect is the Ion gets smaller with increasing core charge. The results of this are the things mentioned in the article.Stone 10:28, 13 February 2006 (UTC)[reply]

The data given under "cause" do not agree with those under "effect." It appears on the face of it that this is because the ionic radius is discussed in the latter section, atomic radius in the former, but the numbers in the "cause" section look wildly different from those I've seen elsewhere (including the Wiki page on atomic radius). It looks like the numbers in the first section are for ionic radius, but I can't find a match for the ones in the second section. I'm loath to edit it myself, because I can't tell exactly what's going on. atakdoug 05:41, 13 April 2007 (UTC)[reply]

No, something is very wrong with this article. The Lanthanide contraction is the theory used to explain why the 5d ionic radii are so similar to the 4d ionic radii. What is described in this article is the basics on why atomic radii differ along a period. —Preceding unsigned comment added by 196.207.35.245 (talk) 08:12, 2 November 2007 (UTC)[reply]

I totally agree totally with the preceding comment. The radius decrease along a group is not typical of the f series (although it might be admitted that it is indeed more consequent, at least considering the Ln³⁺ ions). Unfortunately some textbooks use the term "lanthanide contraction" for this, whereas others use the term to explain the 4d-5d element similarity. Since the contraction itself is not unique, I would recommend using the term only when 4d- and 5d-elements are to be compared, but I'm afraid not everybody agrees. Beryllium-9 (talk) 16:42, 30 October 2009 (UTC)[reply]

I have just checked six texts (Cotton and Wilkinson, Housecroft and Sharpe, Jolly, Huheey, Miessler and Tarr, Porterfield). All say that the lanthanide contraction itself is the decrease in the 4f series, and describe the 4d-5d similarity as an effect or consequence of the lanthanide contraction. I plan to edit the article soon to conform to these texts. Dirac66 (talk) 03:12, 9 November 2009 (UTC)[reply]

One more comment. It is true that the explanation of the lanthanide contraction is just "the basics on why atomic radii differ along a period". The reason it has a special name for the 4f series is because of the importance of its consequences for the post-lanthanide elements and their chemistry. Dirac66 (talk) 03:32, 9 November 2009 (UTC)[reply]

Removed contradict

Whilst adding some content to the intro and a small clarification to the Cause para I have removed the contradict tag as IMHO although the article is not clear I do not think it now contradicts itself. As an aside I was surprised when looking for ionic radii for this article that the wiki data table quotes just one value so I have taken all of the data from Greenwood as a more trustworthy source. Axiosaurus (talk) 19:24, 13 December 2007 (UTC)[reply]

The sentence: "This effect is particularly pronounced in the case of lanthanides, as their 4f subshells are being filled across the period and they are less and less able to shield the outer (5th and 6th) shell electrons" is not explained in the article; there is no common sense reason why increased electron density would decrease electron shielding. In fact, this is counter intuitive, and deserves an explanation. —Preceding unsigned comment added by 75.111.28.97 (talk) 19:31, 2 April 2009 (UTC)[reply]

I have now reworded this sentence. "Less and less able to shield" was incorrect, and I have changed it to "not very effective at shielding". Thank you for pointing out the problem. Dirac66 (talk) 22:28, 2 April 2009 (UTC)[reply]

Actinide contraction?

Is there an actinide contraction in analogy to the lanthanide contraction? And why isn't La in here? The lanthanides are:

57. Lanthanum, La 58. Cerium, Ce 59. Praseodymium, Pr 60. Neodymium, Nd 61. Promethium, Pm 62. Samarium, Sm 63. Europium, Eu 64. Gadolinium, Gd 65. Terbium, Tb 66. Dysprosium, Dy 67. Holmium, Ho 68. Erbium, Er 69. Thulium, Tm 70. Ytterbium, Yb 71. Lutetium, Lu

While the actinides are:

89. Actinium, Ac 90. Thorium, Th 91. Protactinium, Pa 92. Uranium, U 93. Neptunium, Np 94. Plutonium, Pu 95. Americium, Am 96. Curium, Cm 97. Berkelium, Bk 98. Californium, Cf 99. Einsteinium, Es 100. Fermium, Fm 101. Mendelevium, Md 102. Nobelium, No 103. Lawrencium, Lr

So is there an actinide contraction in analogy with the lanthanide contraction? --121.7.203.206 (talk) 10:48, 21 May 2009 (UTC)[reply]

"Actinide contraction" isn't even an article, which you can see from the red links. --121.7.203.206 (talk) 10:50, 21 May 2009 (UTC)[reply]

The first element after the actinides is rutherfordium (Z=104) whose article has no value for atomic radius. I think that atomic radii are unknown for this and subsequent elements because the amounts isolated are too small. If so, then the answer to your question is that there is no data. Not everything is known. Dirac66 (talk) 01:54, 22 May 2009 (UTC)[reply]

Ah, so Dirac66 agrees that the term "lanthanide contraction" is to be used mainly when comparing preceding and subsequent elements with each other? ;) Beryllium-9 (talk) 16:42, 30 October 2009 (UTC)[reply]

Well, I did agree when I wrote the above comment last May. However after reading your question, I checked the textbooks as noted in my last edit a few minutes ago, and it seems I was wrong. The texts in fact agree that the lanthanide contraction is the decrease in radius along the 4f series, and that the 4d-5d similarity is its consequence. As for the question of User 121.7.203.206 which started this section, we should look at the radius of the 5f series (and not succeeding elements such as Rf as I said previously). Housecroft and Sharpe (Inorganic Chemistry, 2nd edn 2005, p.742) give values which gradually decrease from 111 pm for Ac³⁺ to 95 pm for Cf ³⁺ (last element for which they give data), so yes, there is also an actinide contraction. Dirac66 (talk) 03:24, 9 November 2009 (UTC)[reply]

Why does this article use the Ce to Lu definition of lanthanides?

Isn't La a lanthanide too? Double sharp (talk) 14:31, 9 October 2013 (UTC)[reply]

Resolved with the addition of La. Double sharp (talk) 12:55, 10 October 2013 (UTC)[reply]

Obvious musunderstanding here. The contraction is seen in elements heavier than Ce- it isn't a definition of lanthanide but the effect seen within the lanthanides. La itself doesn't have any f electrons! Any way it can't do any harm to extend the definition to include lanthanum as this seeming "contradiction" may cause confusion when the article is first read.Axiosaurus (talk) 15:35, 15 October 2013 (UTC)[reply]

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