Wikipedia:Reference desk/Archives/Science/2018 January 29

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January 29

Electron affinities of the superheavy elements

Have there been any published predictions of EA values for elements with Z > 103 beyond the few (Nh, Mc, Ts, Og, elements 119 and 121) listed at Electron affinity (data page)? Double sharp (talk) 09:54, 29 January 2018 (UTC)

Google Scholar search for predicted electron affinity superheavy gave a bunch of useful-looking refs, including:

• Eliav, Ephraim; Fritzsche, Stephan; Kaldor, Uzi (2015). "Electronic structure theory of the superheavy elements". Nuclear Physics A. 944: 518–550, December 2015, Pages 518-550. doi:10.1016/j.nuclphysa.2015.06.017. Abstract: High-accuracy calculations of atomic properties of the superheavy elements (SHE) up to element 122 are reviewed. The properties discussed include ionization potentials, electron affinities and excitation energies...
• Fricke, Burkhard (1975). "Superheavy elements a prediction of their chemical and physical properties". Recent Impact of Physics on Inorganic Chemistry. Structure and Bonding. Vol. 21. Springer. pp. 89–144. doi:10.1007/BFb0116498. ISBN 978-3-540-37395-7. Discusses elements Z=104–172 and also Z=184 (but I can't access enough to know what properties are covered).

DMacks (talk) 14:15, 29 January 2018 (UTC)

Both papers are very interesting (and I've seen the latter before), but it looks like the only new value given is the EA for Rg (Z = 111, eka-Au) in the first paper. But thank you very much for this help! Double sharp (talk) 06:17, 30 January 2018 (UTC)

@DMacks: I've added the Rg value to the data page; unfortunately no others are given in either article (except for element 171 in the second paper, eka-tennessine, but that is so very far away from what is currently known that even the author only dares to say that his calculations would likely be not "too far away from reality" up to eka-radium, element 120). Double sharp (talk) 14:37, 30 January 2018 (UTC)

Oh, and I found a paper (10.1103/PhysRevA.91.020501) with values for Mc, Lv, and Ts as well. I also see the values for Cn and Fl are predicted to be negative, but I can't find anything saying how negative they ought to be. Double sharp (talk) 15:03, 30 January 2018 (UTC)

Reactivity of ytterbium

With the exception of Yb, the reactivities of the lanthanides increase with size; for example, Eu has the largest metallic radius and corrodes most quickly, followed by La, Ce, Pr, and Nd in about that order (since metallic Eu and Yb have two electrons delocalised per atom while the other lanthanides have three). So why is Yb such a glaring exception? Double sharp (talk) 10:07, 29 January 2018 (UTC)

Ytterbium has a 4f14 6s2 electron configuration; having two complete orbitals is particularly stable and results in low reactivity; this is sometimes called "pseudo-noble-gas configuration" as it is not a true s2 p6 configuration, but it does lead to lower reactivities for elements with it. --Jayron32 13:05, 29 January 2018 (UTC)

The ytterbium article explains metallic radius in terms of having only two delocalized electrons. I would suppose this may be related to the third ionization energies listed in lanthanide (Yb and Eu are particularly high, hence the +2 states). Yb also has a different lattice, though I'm not sure if this matters to the corrosion process. Wnt (talk) 02:50, 30 January 2018 (UTC)

Is there such a thing as "clean" (non-pathogenic) particulate matter?

Greetings!

I've been studying the health effects of particulate matter and am curious about whether some of it may not be harmful; viz., can one engineer microscopic particles that—when inhaled—do not adversely affect people?

Imagine a 100 gram mass of "clean dirt" (for want of a more proper term) evenly ranging in diameter from 400 nanometers at the smallest to 700 nanometers at the largest, thus blocking out visible light rays when scattered in the air. Can such a substance—that would occult visible light and also remain harmless to human physiology—be produced with existing materials science?

Also, assuming that such a substance exists, can it be made to adhere to a magnet (like iron or nickel filings, but non-pathogenic)?

Thank you. Pine (talk) 10:50, 29 January 2018 (UTC)

Probably not. Most particulate pollution affects the lungs based on the size of the particles rather than their composition, i.e. otherwise inert compounds still cause harm due to just being in the lung. Particulate matter as a pollutant is generally classified by particle size alone, without regard for composition of those particles. See here "The size of particles is directly linked to their potential for causing health problems. " --Jayron32 16:41, 29 January 2018 (UTC)

Tell that to the people using them as a drug delivery mechanism. Fgf10 (talk) 19:28, 29 January 2018 (UTC)

Those are 50 nm particles. If you read the article I linked, it notes that <2.5 nm particles are the sizes where it starts to get bad. --Jayron32 20:12, 29 January 2018 (UTC)

Correct, hence your "Probably not" was entirely incorrect. Accuracy and phrasing matter. Also, it's nanometre, not nanomolar Fgf10 (talk) 21:52, 29 January 2018 (UTC)

Point taken. Thanks for clarifying. It also helps to explain, in detail, what the specific error a person makes is, while you are correcting them, so that they know and can correct it. --Jayron32 22:30, 29 January 2018 (UTC)

Just to clarify, one defines PM_2.5 as particulates that are less than 2.5 μm (2,500 nm) in diameter. My question relates to particles evenly ranging in size from 400 nm to 700 nm. Since certain 50 nm particles can be benign—or even beneficial—to people, does that mean that particles large enough to block visible light may also be?

Pine (talk) 08:23, 30 January 2018 (UTC)

It may not be that simple. Ruslik_Zero 20:34, 29 January 2018 (UTC)

There is one common class of particulate matter where the current evidence is fairly ambiguous about whether or not it is harmful. That is sea salt particles. Fine particles of sea salt dissolve in the moisture of the body, but one is unlikely to breathe enough mass to meaningfully change the body's total salt composition. Hence, it is plausible that sea salt particles may be pretty benign. That could be an avenue to consider for your question. If you were thinking about other options, then it pretty much needs to have similar qualities. A substance that easily decomposes into essentially harmless material after it enters the lungs. Dragons flight (talk) 20:31, 30 January 2018 (UTC)

It seems like you're trying to reinvent smoke or even fog. It looks like marijuana can readily be put to the use of producing particles with a median size of 380 nanometers. [1] You could use something else for this application, but ... why? ;) Wnt (talk) 00:18, 1 February 2018 (UTC)