Tag: periodic table

Lithium: a rare earth metal that is lighter than air?

Keith S. Taber

It was purely by accident that I had the radio on when I heard it claimed that

The actual phrase that caught my attentions was

"the lightest metal on earth, lighter in fact than air, lithium".

This seemed bizarre, to say the least.

I went to the BBC website page for the programme concerned (an episode of a series called 'The Scramble for Rare Earths'), where it was acknowledged that a mistake had been made:

"Correction: this episode incorrectly states that lithium is lighter than air. Lithium has a lower atomic mass than oxygen or nitrogen."

So, someone at the BBC had spotted the mistake, or it had already been pointed out to them.

But I thought the correction was interesting in itself, as it made perfect sense to someone who would have the subject knowledge to have noticed the error and appreciated how it came about. I was less sure it would explain much to someone who did not already appreciate the ambiguity of the labels we give to both substances and also to the nanoscopic particles from which the are composed. More on that below, but first there is another clarification needed.

The bearable lightness of beings

Lightness strictly contrasts with heaviness, and so is about weight. Thus the 'old chestnut'1:

which is heavier: a tonne of lead or a tonne of feathers?

Of course, by definition, the mass of a tonne of anything is fixed – so a tonne of feathers has the same mass (and so, in the same gravitational field, the same weight) as a tonne of lead, even if our instinct is that feathers are lighter.

So, really this is about density. When someone (sorry, Misha Glenny) makes the reference:

the lightest metal on earth, lighter in fact than air, lithium

We might respond in various ways:

  1. this is a meaningless comparison as without knowing how much of each we are comparing it is not possible to draw any conclusion (a great deal of air would be heavier than a tiny amount of lithium);
  2. to make sense of this we must assume we are considering the same amount of each; or
  3. yes, that seems reasonable: the lithium metal on earth weighs less than the air.

Option 1 is clearly a pedantic response – 'we will not assume something you do not tell us: it is not for us to add necessary information you have omitted'. Now this would be my response, but then I know I have a mind which tends to such pedantry. I would like to think this is due to my scientific training but actually think it predates that. Perhaps I am just a pedantic person.

Option 3 follows a line of argument that as we have not been told how much is being considered, then the only admissible assumption from the claim is this refers to the earth ("metal on earth"). Lithium is a reactive element (which is why it is stored under oil to avoid oxygen reaching the surface – see the image below), not found native, so any lithium metal on earth is the result of deliberate processing – and, surely, there is much less weight of lithium metal here than the weight of the atmosphere. (However, invoking the earth as a whole complicates the mass:weight relationship, so we would need to specify where we are doing the weighing – say at the earth's surface beneath the atmosphere.) I suspect most people would immediately dismiss this as not being the intended meaning.

The sensible option?

Option 2 would surely be how most people would interpret "lighter than"given the context of the claim. As long as we agree on what we mean by 'the same amount', we have no problem. We have already considered one option which clearly does not work: same amount = same mass.

In chemistry, amount of substance is measured in moles. One mole of lithium weighs about 7 g. But we only apply moles to collections of what we take as identical entities. Lithium metal is comprised of lithium atoms2, and although these atoms are not all identical (natural lithium has a small proportion of 6Li with only three nuclear neutrons mixed with the majority 7Li) they can be assumed near enough so for most purposes.

Air, however, is a mixture of different substances: mainly nitrogen, oxygen and argon, but also including many others in smaller amounts. And its composition is not fixed. In particular, the water vapour levels change a good deal; but also CO2 levels (say, over a forest as opposed to a dessert, even ignoring anthropogenic inputs due to human activity); SO2 levels being higher near active volcanoes; higher nitrogen oxides and ozone levels from car emissions in built up areas; carbon disulphide levels from algae being higher over some sea areas, etc, etc.

But dry air is mostly nitrogen and oxygen, and a mole of nitrogen weighs about 28g and a mole of oxygen about 32g, so a gas mixture which is nearly all nitrogen and oxygen and which contains 'a cumulative mole'* of these gases (say about 0.78 moles of nitrogen and 0.21 moles of oxygen, and a small amount of other atmospheric material) will weigh more than our 7g of lithium.

* But we had to do some violence there to the proper use of the mole concept.

The sharp-eyed will also have noticed that the molar masses of the substances oxygen and nitrogen were based on molecular masses – for the good reason that in the air these substances exist as diatomic molecules. That is, while it is true that "lithium has a lower atomic mass than oxygen or nitrogen" that cannot be a full explanation as atomic mass is not the most relevant factor for these gases. 3

So, 'same amount' cannot be weight, and it is not moles, but rather can sensibly be volume. Volume for volume, a denser material is heavier than a rarer (less dense) one. Sensibly, then, the claim being made in the radio programme/podcast can be understood to be that lithium is less dense than air – thus explaining all those lithium balloons we see floating around.4

photograph of lump of lithium floating in oil.

A sample of the metal lithium in oil (source: wikimedia. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.)

The metal is floating in the oil, showing it has a lower density (is 'lighter') than the oil. However, the metal is clearly not 'lighter than' air.

The chemist's triplet

Now I have rather made a lot of a single broadcast error, that it seems had already been acknowledged (though I doubt more than a very small proportion of radio listeners systematically check out webpages to find out if the programmes they listen to contain any acknowledged errors). But I think what happened here is symptomatic of a core issue in chemistry, and the teaching of chemistry.

This refers to something first widely highlighted by the Glasgow based scholar Prof. Alex Johnstone in 1982, and known as his triangle. Chemistry deals with substances which are handled at bulk scale in the laboratory and explains the proprieties of these substances in terms of models concerning theoretical entities at the nanometre scale: electrons, bonds, ions, molecules, atoms and so forth. Johnstone referred to the 'microscopic' level as opposed to the 'macroscopic level', and so this term is widely used, but a better term might be submicroscopic (or nanoscopic, cf. the nanometre) as single ions and discrete molecules are not even close to being visible under any optical microscope. 5

Further, chemistry has its specialised symbolic language, such that, for example, a chemical reaction would commonly be represented in terms of a reaction equation using chemical formulae. The expert chemist or science teacher moves effortlessly around the macroscopic/microscopic/symbolic apices of this chemist's triangle, but Johnstone strongly argued that classroom presentations that readily moved back and forth between bench phenomena, equations, and talk of molecules, would overwhelm the working memory of the novice learner. (If you are not familiar with the critical notion of working memory, perhaps check out 'how fat is your memory?')

cover of RSC book Johnstone Triangle: The Key to Understanding Chemistry

The Johnstone Triangle

The Key to Understanding Chemistry

The idea of this 'chemist's triplet' (as it is sometimes labelled, borrowing a term from spectroscopy) has been considered the most important factor specific to chemistry pedagogy, and indeed there is at least one whole book on the topic (Reid, 2021).

Johnstone was right to alert science teachers to this issue, although an authentic chemistry education does have to work to move learners to a position where they can interpret and move across the triplet. Chemistry students need to learn to associate phenomena (e.g., burning) with both technical descriptions (e.g., combustion, oxidation) and with molecular level models of what is going on in terms of bond breaking and so forth (Taber, 2013). But learners will need much support and practice, and to be given sufficient time, to develop competence in this ability.

Perhaps a trivial example is moving from the everyday description that, say, mercury is 'heavy' (with only an implied notion of how much mercury we are talking about) to the more technical reference to density, and an explanation based on the micro-structure of mercury in terms of ions (and conduction electrons) in the condensed state.

Figure showing a triangle of experiential level, theoretical-descriptive and theoretical-explanatory levels.
The chemist's triplet (Taber, 2013)

Useful and misleading ambiguity

Part of the challenge for teachers (and so learners) is how key terms can mean different things according to context. So, the labels 'mercury' and 'Hg' can refer to an element in abstract, but they also refer to some of the substance mercury (a macrosopic sample of the element) and to an individual atom of mercury. A chemical equation (such as 2H2 + O2 ⇾ 2H2O) can refer to bulk quantities of substances reacting, but also to individual molecules within the theoretical models used to explain what is going during the reaction.

Often during a chemical explanation the same label ('mercury') or equation (2H2 + O2 ⇾ 2H2O) will be referred to several times, as the focus shifts from macroscopic substance to submicroscopic entities, and back again. This adds to the learning demand, but can also be confusing unless a teacher is very explicit at each point about which is being signified. An ambiguity which can be useful for the fluent, can also be confusing and frustrating for the novice (Taber, 2009).

So, in moving from considering atoms (where lithium has less mass than nitrogen) to substances (where under standard conditions lithium is much more dense than nitrogen) the meanings of 'lithium' and 'nitrogen' change – and perhaps that is what confused journalist Misha Glenny or whoever prepared his script. The experienced science teacher may find this a surprising basic error in a programme from an elite broadcaster like the BBC, but perhaps this is a useful reminder just how easily learners in introductory classes can be confused by the ambiguity reflected in the 'chemist's triplet'.

Read more about this macro-micro confusion

Rare earths – a double misnomer

The radio programme claiming lighter-than-air lithium was part of a short series on 'The Scramble for Rare Earths'. Now 'rare earths' refers to the elements also known as the lanthanides, part of the 'f-block' in the periodic table.

The term 'earth' is also found in the common name of the group of metals, including calcium and magnesium, known as the 'alkaline earths'. 'Earths' is an anachronistic reference to materials such as oxides which were not actually elements. So, the term alkaline earths is misleading as these elements are not 'earths' but the label has become established. (Who would be a chemistry student?)

The 'rare earths' are not earths either, but metallic elements. They are also not all especially rare. They were not initially readily recognised and characterised as different rare earth elements often have similar chemical properties and they occur in the same ores, and so historically they proved difficult to separate and identify. This label of 'rare earth' is then also something of a historical hang-over: although these elements are widely dispersed in the earth's crust so although not actually rare, they are seldom found in highly concentrated sources from which they can be readily extracted.

Rare earths do not seem to be well understood by the lay-person: quite a few websites claim that "quinine contains rare earth compounds" (see 'Would you like some rare earths with that?') As quinine (an antimalarial compound often taken as a 'tonic') is a single chemical substance, it clearly does not contain other compounds: but, in any case, its formula is C20H24N2O2 so its elemental composition is just of hydrogen, carbon, nitrogen and oxygen. Thus the repeated claim about rare earths in quinine seems curious.

The paradox of 'The Scramble for Rare Earths'

But then the BBC's blurb for the radio programme I came across, an episode of 'The Scramble for Rare Earths' called 'The Hidden Paradox', tells us:

"Misha Glenny explores the world of rare earth metals. Reducing CO2 emissions requires critical raw materials like lithium, cobalt and nickel but mining and processing them can pose a serious threat to the environment. Can we solve the paradox?"

Presumably the paradox being that Misha Glenny explores the world of rare earth metals with reference to the alkali metal lithium, and transition elements cobalt and nickel: none of which are rare earths. Perhaps he found the rare earths too rare to include? Perhaps I need to listen to the rest of the programme.

Work cited:
Notes

1 This is an idiom – a phrase which has currency in the language, and has come by convention to have a particular meaning; but where that sense is not clear from the literal meanings of the individual words. An 'old chestnut' is (when it is not a chestnut that is old) something which has been repeated so often it is familiar and loses any impact.

I suspect most readers will have met this question before (or a variation on it) and will not be caught out to suggest the feathers weigh less than the lead.

Read about idioms in science discourse

2 Strictly, solid lithium metal contains an array of Li+ ions in a field of delocalised electrons. No particular electron is associated with any specific lithium ion – they are in molecular orbitals and – being delocalised – do not stay in the same place. So a mole of lithium is a mole of Li+ ions with a mole of (collectively, but not individually) associated electrons. This is just one complication that must make chemistry difficult for learners.

3 We say a mole of lithium is 7g, although this counts the individual 'atoms' (see note 2) even in the solid state where a single metallic crystal could be seen to be more akin to a single molecule. Of course, a mole of lithium crystals would have a mass MUCH more than 7g. Arguably, it is somewhat arbitrary how we define a mole of metallic lithium (and a mole of an ionic solid even more so) compared with a mole of simple molecular substances such as methane or carbon dioxide – but the convention is well established. This is a formalism that could be different – but not if you want to score the marks in a chemistry examination.

4 If lithium was heated to give off vapour, then that vapour would be less dense than air. However lithium is highly reactive and the vapour can only be kept stable in a vacuum or an inert atmosphere (and would only remain a vapour in an atmosphere at a high enough temperature). In the earth's atmosphere any slight leakage from a balloon would likely quickly lead to an explosive failure. Perhaps there is a planet somewhere with a hot enough argon atmosphere where lithium filled balloons could in principle be safely used if a suitable inert material could be found to make the balloon itself – but I doubt this would ever be a preferred option.

5 Arguably, a pure single crystal diamond could be considered a molecule, but that is not what we normally mean by a molecule. Again the choice of how to label different entities is somewhat arbitrary (in the sense that different decisions could rationally have been reached), and learners have to acquire the canonical, historically contingent, labels.

Move over Mendeleev, here comes the new Mendel

Seeking the islets of Filipenka Henadzi

Keith S. Taber

"new chemical elements with atomic numbers 72-75 and 108-111 are supposedly revealed, and also it is shown that for heavy elements starting with hafnium, the nuclei of atoms contain a larger number of protons than is generally accepted"

Henadzi, 2019, p.2

Somehow I managed to miss a 2019 paper bringing into doubt the periodic table that is widely used in chemistry. It was suggested that many of the heavier elements actually have higher atomic numbers (proton numbers) than had long been assumed, with the consequence that when these elements are correctly re-positioned it reveals two runs of elements that should be in the periodic table, but which till now have not been identified by chemists.

According to Henadzi we need to update the periodic table and look for eight missing elements (original image by Image by Gerd Altmann from Pixabay)

Henadzi (2019) suggests that "I would like to name groups of elements with the numbers 72-75 and 108-111 [that is, those not yet identified that should have these numbers], the islets of Filipenka Henadzi."

The orginal Mendeleev

This is a bit like being taken back to when Dmitri Mendeleev first proposed his periodic table and had the courage to organise elements according to patterns in their properties, even though this left gaps that Mendeleev predicted would be occupied by elements yet to be discovered. The success of (at least some) of his predictions is surely the main reason why he is considered the 'father' of the periodic table, even though others were experimenting with similar schemes.

Now it has been suggested that we still have a lot of work to do to get the periodic table right, and that the version that chemists have used (with some minor variations) for many decades is simply wrong. This major claim (which would surely be considered worthy of the Nobel prize if found correct) was not published in Nature or Science or one of the prestigious chemistry journals published by learned societies such as the Royal Society of Chemistry, but in an obscure journal that I suspect many chemists have never heard of.

The original Mendel

This is reminiscent of the story of Mendel's famous experiments with inheritance in pea plants. Mendel's experiments are now seen as seminal in establishing core ideas of genetics. But Mendel's research was ignored for many years.

He presented his results at meetings of the Natural History Society of Brno in 1865 and then published them in a local German language journal – and his ideas were ignored. Only after other scientists rediscovered 'his' principles in 1900, long after his death, was his work also rediscovered.

Moreover, the discussion of this major challenge to accepted chemistry (and physics if I have understood the paper) is buried in an appendix of a paper which is mostly about the crystal structures of metals. It seems the appendix includes a translation of work previously published in Russian, explaining why, oddly, a section part way through the appendix begins "This article sets out the views on the classification of all known chemical elements, those fundamental components of which the Earth and the entire Universe consists".

Calling out 'predatory' journals

I have been reading some papers in a journal that I believed, on the basis of its misleading title and website details, was an example of a poor-quality 'predatory journal'. That is, a journal which encourages submissions simply to be able to charge a publication fee (currently $1519, according to the website), without doing the proper job of editorial scrutiny. I wanted to test this initial evaluation by looking at the quality of some of the work published.

One of the papers I decided to read, partly because the topic looked of particular interest, was 'Nature of Chemical Elements' (Henadzi, 2019). Most of the paper is concerned with the crystal structures of metals, and presenting a new model to explain why metals have the structure they do. This is related to the number of electrons per atom that can be considered to be in the conduction band – something that was illustrated with a simple diagram that unfortunately, to my reading at least, was not sufficiently elaborated.1

The two options referred to seem to refer to n-type (movement of electrons) and p-type (movement of electrons that can be conceptualised as movement of a {relatively} positive hole, as in semi-conductor materials) – Figure 1 from Henadzi, 2019: p2

However, what really got my attention was the proposal for revising the periodic table and seeking eight new elements that chemists have so far missed.

Beyond Chadwick

Henadzi tells readers that

"The innovation of this work is that in the table of elements constructed according to the Mendeleyev's law and Van-den- Broek's rule [in effect that atomic number in the periodic table = proton number], new chemical elements with atomic numbers 72-75 and 108-111 are supposedly revealed, and also it is shown that for heavy elements starting with hafnium, the nuclei of atoms contain a larger number of protons than is generally accepted. Perhaps the mathematical apparatus of quantum mechanics missed some solutions because the atomic nucleus in calculations is taken as a point."

Henadzi, 2019, p.4

Henadzi explains

"When considering the results of measuring the charges of nuclei or atomic numbers by James Chadwick, I noticed that the charge of the core of platinum is rather equal not to 78, but to 82, which corresponds to the developed table. For almost 30 years I have raised the question of the repetition of measurements of the charges of atomic nuclei, since uranium is probably more charged than accepted, and it is used at nuclear power plants."

Henadzi, 2019, p.4

Now Chadwick is most famous for discovering the neutron – back in 1932. So he was working a long time ago, when atomic theory was still quite underdeveloped and with apparatus that would seem pretty primitive compared with the kinds of set up used today to investigate the fundamental structure of matter. That is, it is hardly surprising if his work which was seminal nearly a century ago had limitations. Henadzi however seems to feel that Chadwick's experiments accurately reveal atomic numbers more effectively than had been realised.

Sadly, Henadzi does not cite any specific papers by Chadwick in his reference list, so it is not easy to look up the original research he is discussing. But if Henadzi is suggesting that data produced almost a century ago can be interpreted as giving some elements different atomic numbers to those accepted today, the obvious question is what other work, since, establishes the accepted values, and why should it not be trusted. Henadzi does not discuss this.

Explaining a long-standing mystery

Henadzi points out that whereas for the lighter elements the mass number is about twice the atomic number (that is, the number of neutrons in a nucleus approximately matches the number of protons) as one proceeds through the period table this changes such the ratio of protons:neutrons shifts to give an increasing excess of neutrons. Henadzi also implies that this is a long standing mystery, now perhaps solved.

"Each subsequent chemical element is different from the previous in that in its core the number of protons increases by one, and the number of neutrons increases, in general, several. In the literature this strange ratio of the number of neutrons to the number of protons for any the kernel is not explained. The article proposes a model nucleus, explaining this phenomenon."

Henadzi, 2019, p.5

Now what surprised me here was not the pattern itself (something taught in school science) but the claim that the reason was not known. My, perhaps simplistic, understanding is that protons repel each other because of their similar positive electrical charges, although the strong nuclear force binds nucleons (i.e., protons and neutrons collectively) into nuclei and can overcome this.

Certainly what is taught in schools is that as the number of protons increases more neutrons are needed to be mixed in to ensure overall stability. Now I am aware that this is very much an over-simplification, what we might term a curriculum model or teaching model perhaps, but what Henadzi is basically suggesting seems to be this very point, supplemented by the idea that as the protons repel each other they are usually found at the outside of the nucleus alongside an equal number of neutrons – with any additional neutrons within.

The reason for not only putting protons on the outer shell of a large nucleus in Henadzi's model seems to relate to the stability of alpha particles (that is, clumps of two protons and two neutrons, as in the relatively stable helium nucleus). Or, at least, that was my reading of what is being suggested,

"For the construction of the [novel] atomic nucleus model, we note that with alpha-radioactivity of the helium nucleus is approximately equal to the energy.

Therefore, on the outer layer of the core shell, we place all the protons with such the same number of neutrons. At the same time, on one energy Only bosons can be in the outer shell of the alpha- particle nucleus and are. Inside the Kernel We will arrange the remaining neutrons, whose task will be weakening of electrostatic fields of repulsion of protons."

Henadzi, 2019, p.5

The lack of proper sentence structure does not help clarify the model being mooted.

Masking true atomic number

Henadzi's hypothesis seems to be that when protons are on the surface of the nucleus, the true charge, and so atomic number, of an element can be measured. But sometimes with heavier elements some of the protons leave the surface for some reason and move inside the nucleus where their charge is somehow shielded and missed when nuclear charge is measured. This is linked to the approximation of assuming that the charge on an object measured from the outside can be treated as a point charge.

This is what Henadzi suggests:

"Our nuclear charge is located on the surface, since the number of protons and the number of neutrons in the nucleus are such that protons and neutrons should be in the outer layer of the nucleus, and only neutrons inside, that is, a shell forms on the surface of the nucleus. In addition, protons must be repelled, and also attracted by an electronic fur coat. The question is whether the kernel can be considered a point in the calculations and up to what times? And the question is whether and when the proton will be inside the nucleus….if a proton gets into the nucleus for some reason, then the corresponding electron will be on the very 'low' orbit. Quantum mechanics still does not notice such electrons. Or in other words, in elements 72-75 and 108-111, some protons begin to be placed inside the nucleus and the charge of the nucleus is screened, in calculations it cannot be taken as a point."

Henadzi, 2019, p.5

So, I think Henadzi is suggesting that if a proton gets inside the nucleus, its associated electron is pulled into a very close orbit such that what is measured as nuclear charge is the real charge on the nucleus (the number of protons) partially cancelled by low lying electrons orbiting so close to the nucleus that they are within what we might call 'the observed nucleus'.

This has some similarity to the usual idea of shielding that leads to the notion of core charge. For example, a potassium atom can be modelled simplistically for some purposes as a single electron around a core charge of plus one (+19-2-8-8) as, at least as a first approximation, we can treat all the charges within the outermost N (4th) electron shell (the 19 protons and 18 electrons) as if a single composite charge at the centre of the atom. 2

Dubious physics

Whilst I suspect that the poor quality of the English and the limited detail included in this appendix may well mean I am missing part of the argument here, I am not convinced. Besides the credibility issue (how can so many scientists have missed this for so long?) which should never be seen as totally excluding unorthodox ideas (the same thing could have been asked about most revolutionary scientific breakthroughs) my understanding is that there are already some quite sophisticated models of nuclear structure which have evolved alongside programmes of emprical research and which are therefore better supported than Henadzi's somewhat speculative model.

I must confess to not understanding the relevance of the point charge issue as this assumption/simplification would seem to work with Henadzi's model – from well outside the sphere defined by the nucleus plus low lying electrons the observed charge would be the net charge as if located at a central point, so the apparent nuclear charge would indeed be less than the true nuclear charge.

But my main objection would be the way electrostatic forces are discussed and, in particular, two features of the language:

Naked protons

protons must be repelled, and also attracted by an electronic fur coat…

I was not sure what was meant by "protons must be repelled, and also attracted by an electronic fur coat". The repulsion between protons in the nucleus is balanced by the strong nuclear force – so what is this electronic 'fur coat'?

This did remind me of common alternative conceptions that school students (who have not yet learned about nuclear forces) may have, along the lines that a nucleus is held together because the repulsion between protons is balanced by their attraction to the ('orbiting') electrons. Two obvious problems with this notion are that

  • the electrons would be attracting protons out of the nucleus just as they are repelling each other (that is, these effects reinforce, not cancel), and
  • the protons are much closer to each other than to the electrons, and the magnitude of force between charges diminishes with distance.

Newton's third law and Coulomb's law would need to be dis-applied for an electronic effect to balance the protons' mutual repulsions. (On Henadzi's model the conjectured low lying electrons are presumably orbiting much closer to the nucleus than the 1s electrons in the K shell – but, even so, the proton-electron distance will be be much greater than the separation of protons in the nucleus.)3

But I may have misunderstood what Henadzi's meant here by the attraction of the fur coat and its role in the model.

A new correspondence principle?

if a proton gets into the nucleus for some reason, then the corresponding electron will be on the very 'low' orbit

Much more difficult to explain away is the suggestion that "if a proton gets into the nucleus for some reason, then the corresponding electron will be on the very 'low' orbit". Why? This is not explained, so it seems assumed readers will simply understand and agree.

In particular, I do not know what is meant by 'the corresponding electron'. This seems to imply that each proton in the nucleus has a corresponding electron. But electrons are just electrons, and as far as a proton is concerned, one electron is just like any other. All of the electrons attract, and are attracted by, all of the protons.

Confusing a teaching scheme for a mechanism?

This may not always be obvious to school level students, especially when atomic structure is taught through some kind of 'Aufbau' scheme where we add one more proton and one more electron for each consecutive element's atomic structure. That is, the hydrogen atom comprises of a proton and its 'corresponding' electron, and in moving on to helium we add another proton, with its 'corresponding' electron and some neutrons. These correspond only in the sense that to keep the atom neutral we have to add one negative charge for each positive charge. They 'correspond' in a mental accounting scheme – but not in any physical sense.

That is a conceptual scheme meant to do pedagogic work in 'building up' knowledge – but atoms themselves are just systems of fundamental particles following natural laws and are not built up by the sequential addition of components selected from some atomic construction kit. We can be misled into mistaking a pedagogic model designed to help students understand atomic structure for a representation of an actual physical process. (The nuclei of heavy elements are created in the high-energy chaos inside a star – within the plasma where it is too hot for them to capture the electrons needed to form neutral atoms.)

A similar category error (confusing a teaching scheme for a mechanism) often occurs when teachers and textbook authors draw schemes of atoms combining to form molecules (e.g., a methane molecule formed from a carbon atom and four hydrogen atoms) – it is a conceptual system to work with the psychological needs for students to have knowledge built up in manageable learning quanta – but such schemes do not reflect viable chemical processes.4

It is this kind of thinking that leads to students assuming that during homolytic bond fission each atom gets its 'own' electron back. It is not so much that this is not necessarily so, as that the notion of one of the electrons in a bond belonging to one of the atoms is a fiction.

The conservation of force conception (an alternative conception)

When asked about ionisation of atoms it is common for students to suggest that when an electron is removed from an atom (or ion) the remaining electrons are attracted more strongly because the force for the removed electron gets redistributed. It is as if within an atom each proton is taking care of attracting one electron. In this way of thinking a nucleus of a certain charge gives rise to a certain amount of force which is shared among the electrons. Removing an electron means a greater share of the force for those remaining. This all seems intuitive enough to many learners despite being at odds with basic physical principles (Taber, 1998).

I am not deducing that Henadzi, apparently a retired research scientist, shares these basic misconceptions found among students. Perhaps that is the case, but I would not be so arrogant as to diagnose this just from the quoted text. But that is my best understanding of the argument in the paper. If that is not what is meant, then I think the text needs to be clearer.

The revolution will not be televised…

In conclusion, this paper, published in what is supposedly a research journal, is unsatisfactory because (a) it makes some very major claims that if correct are extremely significant for chemistry and perhaps also physics, but (b) the claims are tucked away in an appendix, are not fully explained and justified, and do not properly cite work referred to; and the text is sprinkled with typographic errors, and seems to reflect alternative conceptions of basic science.

I very much suspect that Henadzi's revolutionary ideas are just wrong and should rightly be ignored by the scientific community, despite being published in what claims to be a peer-reviewed (self-describing 'leading international') research journal.

However, perhaps Henadzi's ideas may have merit – the peer reviewers and editor of the journal presumably thought so – in which case they are likely to be ignored anyway because the claims are tucked away in an appendix, are not fully explained and justified, and do not properly cite work referred to; and the text is sprinkled with typographic errors, and seems to reflect alternative conceptions of basic science. In this case scientific progress will be delayed (as it was when Mendel's work was missed) because of the poor presentation of revolutionary ideas.

How does the editor of a peer-reviewed journal move to a decision to publish in 4 days?
Let down by poor journal standards

So, either way, I do not criticise Henadzi for having and sharing these ideas – healthy science encompasses all sorts of wild ideas (some of which turn out not to have been so wild as first assumed) which are critiqued, tested, and judged by the community. However, Henadzi has not been well supported by the peer review process at the journal. Even if peer reviewers did not spot some of the conceptual issues that occurred to me, they should surely have noticed the incompleteness of the argument or at the very least the failures of syntax. But perhaps in order to turn the reviews around so quickly they did not read the paper carefully. And perhaps that is how the editor, Professor Nour Shafik Emam El-Gendy of the Egyptian Petroleum Research Institute, was able to move to a decision to publish four days after submission.5

If there is something interesting behind this paper, it will likely be missed because of the poor presentation and the failure of peer review to support the author in sorting the problems that obscure the case for the proposal. And if the hypothesis is as flawed as it seems, then peer review should have prevented it being published until a more convincing case could be made. Either way, this is another example of a journal rushing to publish something without proper scrutiny and concern for scientific standards.

Works cited
Footnotes:

1 My understanding of the conduction band in a metal is that due to the extensive overlap of atomic orbitals, a great many molecular orbitals are formed, mostly being quite extensive in scope ('delocalised'), and occurring with a spread of energy levels that falls within an energy band. Although strictly the molecular orbitals are at a range of different levels, the gaps between these levels are so small that at normal temperatures the 'thermal energy' available is enough for electrons to readily move between the orbitals (whereas in discrete molecules, with a modest number of molecular orbitals available, transitions usually require absorption of higher energy {visible or more often} ultraviolet radiation). So, this spread of a vast number of closely spaced energy levels is in effect a continuous band.

Given that understanding I could not make sense of these schematic diagrams. They SEEM to show the number of conduction electrons in the 'conduction band' as being located on, and moving around, a single atom. But I may be completely misreading this – as they are meant to be (cross sections through?) a tube.

"we consider a strongly simplified one- dimensional case of the conduction band. Option one: a thin closed tube, completely filled with electrons except one. The diameter of the electron is approximately equal to the diameter of the tube. With such a filling of the zone, with the local movement of the electron, there is an opposite movement of the "place" of the non-filled tube, the electron, that is, the motion of a non-negative charge. Option two: in the tube of one electron – it is possible to move only one charge – a negatively charged electron"

Henadzi, 2019, p.2

2 The shell model is a simplistic model, and for many purposes we need to use more sophisticated accounts. For example, the electrons are not strictly in concentric shells, and electronic orbitals 'interpenetrate' – so an electron considered to be in the third shell of an atom will 'sometimes' be further from the nucleus than an electron considered to be in the fourth shell. That is, a potassium 4s electron cannot be assumed to be completely/always outside of a sphere in which all the other atomic electrons (and the nucleus) are contained, so the the core cannot be considered as a point charge of +1 at the nucleus, even if this works as an approximation for some purposes. The effective nuclear charge from the perspective of the 4s electron will strictly be more than +1 as the number of shielding electrons is somewhat less than 18.

3 Whilst the model of electrons moving around the nucleus in planetary orbits may have had some heuristic value in the development of atomic theory, and may still be a useful teaching model at times (Taber, 2013), it seems it is unlikely to have the sophistication to support any further substantive developments to chemical theory.

4 It is very common for learners to think of chemistry in terms of atoms – e.g., to think of atoms as starting points for reactions; to assume that ions must derive from atoms. This way of thinking has been called the atomic ontology.

5 I find it hard to believe that any suitably qualified and conscientious referees would not raise very serious issues about this manuscript precluding publication in the form it appears in the journal. If the journal really does use peer review, as is claimed, one has to wonder who they think suitable to act as expert reviewers, and how they persuade them to write their reports so quickly.

Based on this, and other papers appearing in the journal, I suspect one of the following:

a) peer review does not actually happen, or

b) peer review is assigned to volunteers who are not experts in the field, and so are not qualified to be 'peers' in the sense intended when we talk of academic peer review, or

c) suitable reviewers are appointed, but instructed to do a very quick but light review ignoring most conceptual, logical, technical and presentation issues as long as the submission is vaguely on topic, or

di) appropriate peer reviewers are sought, but the editor does not expect authors to address reviewer concerns before approving publication, or possibly

dii) decisions to publish sub-standard work are made by administrators without reference to the peer reviews and the editor's input

An element needs a certain number of electrons

An element needs a certain amount of electrons in the outer shell

Keith S. Taber

Bert was a participant in the Understanding Science project. In Y10 Bert was talking about how he had been studying electrolysis in class. Bill had described electrolysis as "where different elements are, are taken out from a compound", but it transpired that Bert thought that "a compound is just a lot of different elements put together"*. He seemed to have a tentative understanding that electrolysis could only be used to separate elements in some compounds.

if they're positive and negative then they would be able to be separated into different ones.

So some things are, some things aren't?

Yeah, it matters how many electrons that they have.

Ah. [pause, c.3s] So have you got any examples of things that you know would definitely be positive and negative?

Well I could tell you what happens.

Yeah, go on then.

Well erm, well if a, if an element gives away, electrons, then it becomes positive. But if it gains, then it becomes negative. Because the electrons are negative, so if they gain more, they just go a bit negative.

Yeah. So why would an element give away or gain some electrons? Why would it do that?

Because erm, it needs a certain amount of electrons in the outer shell. It matters on what part of the periodic table they are.

Okay, let me be really awkward. Why does it need a certain number of electrons in the outer shell?

[Pause, c.2 s]

Erm, well, I don't know. It just – 

So Bert thought that an element "needs a certain amount of electrons in the outer shell" depending upon it's position in the periodic table, but he did not seem to recall having been given any reason why this was. The use of the term 'needs' is an example of anthropomorphism, which is commonly used by students talking about atoms and molecules. Often this derives from language used by teachers to help humanise the science, and provide a way for students to make sense of the abstract ideas. If Bert comes to feel this is a sufficient explanation, then talk of what an element needs can come to stand in place of learning a more scientifically acceptable explanation, and so can act as a grounded learning impediment.

References to atoms needing a certain number of electrons is often used as an explanatory principle (the full shells explanatory principle) considered to explain why bonding occurs, why reactions occur and so forth.

Bert's final comment in the short extract above seems to reflect a sense of 'well that's just the way the world is'. It is inevitable that if we keep asking someone a sequence of 'well, why is that' question when they tell us about their understanding of the world, they eventually reach the limits of their understanding. (This tendency has been labelled 'the explanatory gestalt of essence'.) Ultimately, even science has to accept the possibility that eventually we reach answers and can not longer explain further – that's just the way the world is. Research suggests that some students seem to reach the 'it's just natural' or 'well that's just the way it is' point when teachers might hope they would be looking for further levels of explanation. This may link to when phenomena fit well with the learner's intuitive understanding of the world, or tacit knowledge.

Bert's reference to an element needing a certain amount of electrons in the outer shell also seems to confuse description at two different levels: he explicitly refer to substance (element), when he seems to mean a quanticle (atom). Element refers to the substance, at the macroscopic level of materials that can be handled in the laboratory, whilst an atom of the element (which might better be considered to gain or lose electrons) is part of the theoretical model of matter at a submicroscopic level, used by chemists as a basis for explaining much macroscopic, observed behaviour of samples of substances.