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The NPR News podcast and transcript The Convoluted Story Of How The First Atoms Of Tennessine Were Created includes the following exchange between science reporter Joe Palca and Oak Ridge nuclear engineer Julie Ezold:

PALCA: In other words, in five months, they only got six atoms of tennessine. When I first heard that name, I thought it was a mistake. All the other synthetic elements ended in -ium - think plutonium or americium. Oak Ridge nuclear engineer Julie Ezold understands my confusion.

JULIE EZOLD: We all thought it was going to be that way as well. But remember - the periodic table has rules.

PALCA: Ezold says Element 117 fits in a column of the periodic table filled with compounds called halogens - fluorine, chlorine, bromine.

EZOLD: Therefore, its name had to end in -ine. So instead of tennessium (ph), it's tennessine.


The more I thought about this, the more I questioned how elements discovered in the future might or might not be classified as halogens, especially if an "island of stability" is ever found and even more elements are discovered.

  • Is there really a rule or at least a firm guideline that ultimately requires the name of element 117 to end in -ine simply because it has 117 electrons?
  • Or was it somehow necessary to experimentally demonstrate some chemical property associated with halogens?
  • Or would an atom with 117 electrons certainly and without question behave like a halogen?
  • Or will all current and future elements that obeys certain numerical rules be called halogens no matter how they behave chemically?
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    $\begingroup$ It's worth noting that we see the same thing with element 118: it falls in the noble gas group and, consistent with this, ends in -on instead of -ium: oganesson. See: en.wikipedia.org/wiki/Systematic_element_name $\endgroup$
    – theorist
    Dec 7, 2019 at 4:47
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    $\begingroup$ It comes after Astatine so it is a kind of halogen, in the sense that it has expected valence configuration ns2np5. It is expected to be rather metallic/metalloid. $\endgroup$
    – Alchimista
    Dec 7, 2019 at 8:49
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    $\begingroup$ It is thought that tennessine will have very different chemistry from the lighter halogens. Astatine would already be something of an oddball, if only it could be isolated in reasonable amounts. The discontinuity of the chemical properties between the last common halogen (iodine) and tennessine would be very stark indeed. $\endgroup$ Dec 7, 2019 at 21:04

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Is it tennessINE because it has 117 electrons or because it behaves like a halogen? ... Or will all current and future elements that obeys certain numerical rules be called halogens no matter how they behave chemically?

Yup, that last bit is the most correct. The math and physics behind how electrons form orbitals meant that scientists already knew that Element-117 was going to be one-electron-shy of filling that outermost shell of valence electrons (and they knew it for decades before they were actually able to synthesize it in a lab).


[Tennessine has a -INE name like all the other halogens. Did they test whether it actually acts like 'a halogen'? Or is it simply assumed to behave like the rest? Or does it get to be an honorary halogen just because its electron configuration shoehorns it into the same column as others?]

The half-life for the Tennesine-293 isotope are only about 25ms (and 51ms for Ts-294). That is only really enough time to see how the atom continues traveling through the particle accelerator and tracking the pieces after it decays (to make sure all the masses add up correctly). It is not enough time to do the kind of "real chemistry" of testing whether Tennessine "acts like a proper halogen".

So, is it assumed/calculated to behave like the other halogens? Well that depends what you mean exactly. Fluorine, Chlorine, Bromine and Iodine are all "Non-Metals" whereas Astatine might be a "Metaloid". Tennessine is likely to be even more-so metallic than Astatine - being either a definite "Metaloid" or maybe even a full-on "Metal". One could possibly argue that being a metal disqualifies it from being a 'proper' halogen (while still being Group-17)... but Astatine has been skating by on its shaky credentials since the 1940s so it's probably fine to let them both keep the -INE names. Also, it's not like folks are all that strict about differentiating 'proper' Chalcogens or 'proper' Pnictogens, so why start now with 'proper' Halogens? Sure, it is a bit of a subjective judgement call, but most of the chemistry world is on board with it.


... I questioned how elements discovered in the future might or might not be classified as halogens, especially if an "island of stability" is ever found and even more elements are discovered.

This might be trickier to answer. Part of the reason why scientists were so easily able to just fit Tennessine into the modern table was because Period-7 follows the same pattern of orbitals as Period-6. Period-6 elements mostly have stable isotopes so this essentially gave a mostly-complete template for what the Period-7 row should also look like. (And it worked like a charm as scientists filled out the gaps in the Actinide series and the gaps in the heaviest transitions metals from like 1930 to now.)

We have zero examples of elements in Period-8, so we can only hypothesize that there is a g-block of orbitals that gets added on. Assuming that is all correct, the expected number of s/p/d/f/g electrons needed to fill a Period-8 shell means that the next 'halogen' element would need to have an atomic number of about 167-171... which is a long way off if only fleeting unstable isotopes are left to discover.

If there is an "Island of Stability" then we might luck out and be able to learn more about the electron configuration of Period-8 enough to either keep the g-block idea or scrap it for something better based on that new evidence... but either way you look at it, another new halogen seems unlikely anytime soon.

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    $\begingroup$ I vaguely remember that there is an equation which predicts the maximum atomic number any hypothetical element could have. But I clearly remember that limit is quite lower than the estimated atomic number of the next possible halogen. $\endgroup$ Mar 22, 2023 at 10:12
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    $\begingroup$ @Priyansh2003 I think I saw a $2n^2$ pattern mentioned somewhere while googling all of this that describes the (2, 8, 18, 32...) pattern of the (K,L,M,N...) shells which would mean an O-shell of 50 pins the next Noble Gas at 168. But en.wikipedia.org/wiki/Extended_periodic_table seems to indicate that the latest simulations favor the idea of a Noble Gas occurring at 172 (if I understood correctly, due to relativistic effects letting more electrons squeeze into the shell that would normally be allowed by the $2n^2$ rule). $\endgroup$
    – DotCounter
    Mar 22, 2023 at 14:43
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    $\begingroup$ Excellent answer +1. Iodine already shows incipient metallic character as bonding is becoming delocalized in the solid. For tennessine, Syysziński (pp. 139-146) reports that a compound with nihoinum would have negative charge on the nihonium. $\endgroup$ Mar 24, 2023 at 12:44
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Tennessine was named after the land of Tennessee in USA. The element was created by a joint team of Russian and American researchers. When it was finally confirmed to have recreated by a collaboration of German and American scientists, IUPAC and IUPAP handed over the right to name the element to the former team of discoverers. They suggested to name it Tennessine after the land of Tennessee in USA.

The element's name ends with -ine instead of -ium probably because it is in group 17 all of whose elements are non-metals as names of most metals preferentially ends with a -ium.

It's not possible as of yet to determine its experimental properties given that only six atoms of Tennessine have been created. This is why we can't establish its chemical similarities or dissimilarities with other halogens.

Future elements can be named in many other ways that we don't yet know but maybe scientists would prefer to keep certain trends because periodic table is intended to show patterns and rules.

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    $\begingroup$ Thank you for your answer! I'm still wondering; as discussed in my question, how does one know that element 117 is in group 17? Were any halogenic properties used to isolate the atoms, or is this from some calculation, or from some simple rule? $\endgroup$
    – uhoh
    Mar 20, 2023 at 19:22
  • $\begingroup$ The main criteria to put it in Group 17 is it's electronic configuration ns²np⁵. It matches with general outer configuration of halogens - 7s²7p⁵. $\endgroup$ Mar 21, 2023 at 6:38
  • $\begingroup$ Got it, I guess this is something that a chemist would know intuitively starting with the number 117. $\endgroup$
    – uhoh
    Mar 21, 2023 at 6:48
  • $\begingroup$ Probably, because all halogens, including Tennessine ends with a -ine. $\endgroup$ Mar 21, 2023 at 6:51
  • $\begingroup$ I guess I'm still trying to understand how one starts with 117 and arrives at 7s²7p⁵ with sufficient certainty to call it a halogen. To my question "Is it tennessINE because it has 117 electrons or because it behaves like a halogen?" I think your answer is "It's -ine because it has 117 electrons, which means we expect its configuration to be 7s²7p⁵ which would then mean it's a halogen which would then mean we'd use -ine." Is that a fair summary of your answer? $\endgroup$
    – uhoh
    Mar 21, 2023 at 7:25

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