exchemist

OK, regarding weighing atoms - and thereby the protons and neutrons that make them up - this comes down to knowing what number of atoms there are in a given weight of substance. Avogadro's number is the standard number used in chemistry. It defines what is called a "mole" of the substance. ("Mole" comes from German "Mol", which was a term derived from "molecule"). One mole of any substance contains 6.02 x 10²³ molecules of it (or atoms of it if it is an element). This extremely large number is Avogadro's Number. The number is chosen such that the weight in grammes of one mole is equal to the atomic (or molecular) weight of the substance. For example, one mole of carbon weighs 12g and contains 6.02 x 10²³ carbon atoms. (If you look it up you will see the atomic weight of carbon is 12.) One mole of water contains 6.02 x 10²³ molecules and weighs (2 x 1 + 16) = 18g, because its formula is H₂O, and the atomic weight of H is 1 and that of O is 16. It is very important to know the number of moles of a substance when considering chemical reactions, because that determines the proportions that will react together. For instance, taking water again, the formula H₂O means that 2 atoms of hydrogen are combined with one of oxygen in each water molecule. So in, say, the combustion of hydrogen, which produces water, 2 moles of hydrogen atoms will require one mole of oxygen atoms. In terms of weight, every 2g of hydrogen will take up 16g of oxygen. So when you do a lab reaction, you can weigh out the proportions you need and not have unreacted material left over at the end. Coming back to protons and neutrons, In practice, nobody tries to express the mass of a proton or a neutron in grammes. But from the above I hope you can see we do have the relationship between the number of protons and neutrons in an atom and the weight of a set number of them in grammes, via the mole and Avogadro's Number. There is a nice little write-up here of how Avogadro's Number came to be determined: https://www.scientificamerican.com/article/how-was-avogadros-number/ Admittedly it refers to a number of other pieces of physics and chemistry, but that's the way with science: everything is interlinked and feeds off other stuff. So to learn it there are times when you have to decide not to follow up all the loose ends at once, or you risk getting lost in a swamp of information. I'll come back to the question of ions separately, so that we can keep these strands of Q&A apart. Actually this is doubtful. A flame test requires a steady, non-luminous flame. This became available for the first time in the mid c.19th with the Bunsen burner.

Partly right but not the whole story in my view. Classic Trump behaviour includes floating outrageous ideas and letting them lie for bit, while the Overton window is shifted by his tame news media and political outriders, and then returning to them later with more seriousness. This Canada one may indeed go nowhere, but I think it would be a mistake to count on it being merely a distraction technique.

This reads like word salad: https://en.wikipedia.org/wiki/Word_salad Impossible to comment on its content, as none is discernible.

I’m going to break up the replies so we don’t get a lot of hares running in different directions. First, Lavoisier didn’t have anything like spectrometer, back in the 1780s. He would have recognised phosphorus from its physical and chemical properties, as was done for all chemical substances before spectroscopy became an analytical tool, which was in the 1st half of the c.20th. I’ll come back to the discovery of protons and neutrons later. But as to the question of weight of atoms, that comes down to weighing a sample of a substance and working out how many atoms are present in the sample. For that we need to introduce the concept of Avogadro’s Number, which is extremely important in chemistry and deserves its own post. So I’ll come back to that a bit later today, too.

Ah, but that's just because they don't yet know they want it. False consciousness and all that. 🤪 Autocratic zealots have all the answers........

Das ist nicht nur nicht richtig; es ist nicht einmal falsch.

I like these questions. When one is familiar with an area of science it is easy to ignore the original basis of the concepts one uses all the time. Some of these questions force me to go back and review the history of it all, which is informative. 🙂 OK, a reactant is something that takes part in a chemical reaction. For instance if you burn hydrogen, it reacts with oxygen and produces water: 2H₂ + O₂ -> 2H₂O. Hydrogen and oxygen molecules, shown on the left hand side of the chemical equation are the reactants and water, shown on the right, is the product of the reaction. So one quite commonly speaks of reactants and products. Yes good balances were available, as they were needed by gold and silversmiths for assay purposes. Joseph Black seems to have been the first to use one for chemical purposes at the end of the c.18th. He had one that was accurate to 0.1g, apparently. So by the mid c.19th I expect they had them good for 0.01g or so, which is fine for the sort of thing they were doing. Re phosphoric acid, Lavoisier would obviously have known he had made an acid derived from phosphorus. But the modern term phosphoric acid probably would not have been applied to it until later. Regarding atomic weight, you will see that shown for each element on the periodic table, along with atomic number. It works like this: Atomic number denotes the number of protons in the nucleus. In a neutral atom this is the same as the number of electrons. When it comes to atomic weight, electrons are so light their mass is negligible, at least in chemistry. What counts for atomic weight is the numbers of protons and neutrons in the atomic nucleus. Protons and neutrons weigh almost the same and the number of neutrons in a typical nucleus is normally about the same as the number of protons, though with some variation. So the atomic weight is generally about double the atomic number. Atomic weight is quoted in units of protons or neutrons. For example the atomic number of oxygen is 8. The atomic weight, on the table I linked to in my earlier post, is given as 15.999, so almost 16 but not quite. The reason why it is not exactly 16 is because although almost all oxygen atoms have 8 neutrons, a very small proportion have a different number. The number shown in the table is an average. (These nuclei with different numbers of neutrons are different "isotopes" of oxygen, from the Greek for "same place", i.e. they have different masses but occupy the same place in the periodic table. That is because, so long they all have 8 protons, and therefore 8 electrons, they have identical chemical behaviour - which is what defines them as the element "oxygen". ) This post is getting long, so I'll start a new one about ions. Right, ions. An ion is an atom in which the number of electrons is not the same as the number of protons in the nucleus. That means it will have a net electrical charge, +ve if it has fewer and -ve if it has more electrons than needed for electrical neutrality. I gave an example earlier with H⁺. This is a hydrogen atom with its one electron taken away, leaving just a proton. (If you've ever had an ulcer, you may have been prescribed a "proton pump inhibitor". This just means something that inhibits the mechanism in the stomach that secretes acid, so fewer protons, or hydrogen ions (H⁺) are produced.) You can have ionic compounds: common salt is one. It consists of equal numbers of +ve sodium ions and -ve chloride ions, which attract one another and form a regular pattern in a crystal of salt. Both of these have lost or gained one electron per atom, but higher numbers are possible, depending on the element , e.g. Ca²⁺ or O²⁻ . One way you know you have got ions is if you dissolve the substance in water and see if it conducts electricity. Salt water conducts well, because +ve sodium (Na⁺) ions are attracted to the -ve wire and chloride (Cl⁻) ions to the +ve one, so a current can flow. (By the way the chemical symbol for sodium, slightly annoyingly, is Na, from the Latin natrium. The word originally comes from Wadi El Natrun in Egypt, where natural deposits of sodium carbonate are to be found. As Michael Caine would say, "Not many people know that".)

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By 1875 they had a pretty good idea of how to characterise chemical compounds. Mendele'ev's periodic table came out in 1871. The basic way the c.19th chemists worked was by careful measurements of weight changes. They weighed the reactants and the products and from this were able, eventually, to work out the atomic weight of each element. Once they knew the atomic weights, they could use weight changes during reactions to establish the chemical formula for each substance. It all started back in the time of Lavoiser, at the end of the c.18th (he lost his head in the French Revolution, in fact, poor fellow). He studied combustion, through which he was able to find out things like the fact that when you burned something it absorbed only 20% of the volume of air available. So that told him there were 2 components in air, the 80% component being inert. He called it "azote", from the Greek for lifeless, which is French for nitrogen to this day. He also found the ash from burning phosphorus weighed more than the phosphorus before burning, and that this ash was acid when dissolved in water. So he realised the component of air that reacted had become part of the ash, along with the phosphorus - a chemical compound. Because the ash was acid he called the reacting component of air "oxygene", from the Greek for acid-generating. What he had made was phosphorus pentoxide P₂O₅, and when he dissolved it, he got a solution of phosphoric acid. (Lavoiser was subsequently shown to be wrong in associating oxygen with acidity, when hydrochloric acid was shown not to have any oxygen in it. In modern chemistry, acids are substances that release hydrogen ions, H⁺, in solution. So it was 2 steps forward, one step back.) It was by painstaking experiments like this, carefully weighting reactants and products, or carefully measuring volume changes in the case of gases, that by degrees the identities of chemical elements and compounds and their formulae came to be discovered, from the proportions in which they reacted.

Marketing was the key to the success of the cars, though. History is littered with great designs that don't get to market effectively. And the rocket business was the result of his inspiration and drive, even though obviously he was not a rocket designer himself. He's not just rich, he has put his money to work in a very unique way and very effectively. None of which stops him having turned into a Nazi, of course.............. (I feel like Bryan Ferry, who famously got into terrible trouble for pointing out the Nazis had fantastic iconography. 😄)

But it was Musk's business that took it to market, was it not?

He made electric cars sexy and showed that Gerry Anderson had the right idea about rockets. Both fantastic achievements. But then he went mad after his son changed gender and disowned him, started to live in a far-right bubble, raving about the "woke mind virus" and has morphed into a megalomanic Nazi.

Yeah and there is an arid city on the top of Ben Nevis, right? 😄 In fact I have only been up it once, on a May bank holiday in the 1990s. It was 22C in the glen at the bottom and we heard a cuckoo. At the top it was snow.

Very interesting indeed. Lovely to see a simple idea like this can be practical. However it has to be recognised that this only works where there are regular fogs. The W coast of S America is special in that it has the cold Humboldt current coming up from the Antarctic, which forms fogs with regularity. I don't think this idea would be very transferable to other regions.

OK, hydrazine. This is N₂H₄, https://en.wikipedia.org/wiki/Hydrazine so made of molecules each of which has 2 atoms of nitrogen, joined by a single chemical bond N-N and with each nitrogen atom also being to joined by a bond to 2 hydrogen atoms. The astronauts and rocket scientists know what it is because it is made for them in a chemical plant, but if your question is how can someone , in principle, test this stuff to confirm its identity, then I think one would probably have a look at its infra-red spectrum. Molecules like this absorb infra red radiation at particular frequencies, according to the atoms present and how they are bonded. (The bonds are stretchy, so if the atoms are pulled apart or pushed together, the bond can be set into vibration, the frequency of which depends on the mass at either end and the strength of the bond. Infra red waves of the exact frequency required can pull or push them in this way and when they do the molecule absorbs some of the radiation, which the spectrometer can detect.) But your more general question is really about analytical chemistry as a whole. This is a big subject. The various forms of spectroscopy, one of which I have described above, play a big role in helping to identify chemical compounds. But there are also other methods which often involve trying to carry out chemical reactions to see what results. Normally this only works when you already have some idea of what you are looking for. I think your last question, about Mg and the significance of the number 12, actually gets us to an excellent starting point for some understanding of chemistry, because it gets us to the Periodic Table of the elements. Here's a link to one I use for reference: https://ptable.com/#Properties Mg is the chemical symbol for magnesium and it is the 12th element in the table. 12 is its "atomic number". And you are right, the atom has 12 electrons, to balance the 12 positively charged protons in its nucleus. Chemistry is all about the electrons in the atom: electrons are what form chemical bonds. The number of electrons in atoms of the various elements determines how each element will behave, chemically. Mendele'ev, who originally designed the Table in the c.19th, did so without knowing this (!). He just observed there were similarities in the chemical behaviour of certain elements and grouped those into columns. So for example, the column at far left with lithium, sodium etc. are all very reactive, soft metals which react with, say chlorine to form white salts with one atom of chlorine per atom of metal. (Common salt NaCl is one example.) The next group, with Mg, Ca etc in it, also form white salts but with two atoms of chlorine per metal atom. So he realised there is something important in common between Li and Na, and between Mg and Ca. The rest of the table was built up in similar fashion, from knowledge of the reactions of elements and the compounds they tended to form. Nowadays we know it is to do with the way electrons build up in layers ("shells") like an onion, as one moves from lighter to successively heavier atoms, so that repeating patterns come back over and over when the shells are similar. This is something we can discuss. Elements with higher atomic number have more mass, so as one reads the table starting at the top left, one gets a progression of successively heavier atoms. The table is divided nowadays into blocks, according to the types of properties one finds in the columns (known as periodic table Groups). Again, this is something we can discuss. If you click on an element in the version of the table I have linked, you will get on the left a rather technical summary of key data but also, probably more interesting to you, a blue link to a Wiki text article all about the element.I suggest having a look at magnesium, since you asked about it, and perhaps also nitrogen, since you asked about hydrazine.

Not at all. A lot of well-informed and intelligent Americans have great faith in the robustness of their constitution and its ability to self-correct, given time. But I think this is complacent. These Project 2025 people have worked out how to neuter it. And what they are doing will be extremely hard to reverse, especially the loss of trust among the population in the institutions of the state, including the law. That is a recipe for cynicism, corruption and anarchy.

Ukraine does have some rare earth deposits, at least according to Reuters: https://www.reuters.com/markets/commodities/what-are-ukraines-rare-earths-why-does-trump-want-them-2025-02-05/ though apparently they are not yet being mined. But I’m sure you are right that Trump won’t grasp the distinction between these various minerals. As for my scenario being worst case, yes it is, but experience of this blitzkrieg approach to date, plus consideration of how previous coups in history have proceeded, convinces me one needs to plan and act on the worst case basis to have any hope of not being taken by surprise by it. I think there’s a good chance the mid term elections will be distorted in various ways. We’ve seen it already in some states. If the courts are ignored, which is an idea they are already testing, who is to stop them? There are already rumblings about Trump trying for a 3rd term. All this is classic authoritarian stuff. Anyone who still can’t see where this is heading has his head in the sand, in my view. You’d have to ask Trump. He is the one already suggesting it.

Welcome, and ask away! It may save time if you can read a bit on each issue, e.g. by scanning at least part of a Wikipedia article or something, first and then ask the questions about the parts you don't understand. (I say "part" because I realise these articles tend to plunge into a lot of detail, using possibly unfamiliar terms.)That way, people here don't have to recite a lot of stuff that is readily available on the internet. There are one or two other good sources we can direct you to as well, if necessary. But we can see how it goes.

The first step, surely is for independent-minded people and what remains of the independent press to stop being mealy-mouthed and deferential and call it what is it: an authoritarian coup (a "soft coup", because it the army is not participating). I was pleased to see Martin Wolf in yesterday's Financial Times saying this for the first time. He also articulated, for the first time in print, my own suspicions that in future free and fair elections must now be in doubt. Wolf also sees this as an example of "state capture", in this case by the tech barons. None of this is what people elected Trump to do. It is Project 2025, which Trump disavowed on the campaign trial but is now in full swing, with Trump having appointed its leading lights to powerful positions and executing its programme.

.....and Gaza. I think you are right: he sees everything in terms of his notions of business, which are largely those of a real estate crook, and through the lens of global competition with China. Territorial acquisition is very much to his taste. Even in the case of Gaza, he sees it in terms of a real estate play, for building seaside casinos and hotels. The ethnic cleansing of 2 million poverty-stricken people from their ancestral homeland - not to mention the issue of where the hell they would go, if they are not exterminated by the IDF - is of zero concern. With similar lack of concern for its population and nationhood, he has thrown Ukraine and its brave leader under a bus. That's because he wants the war to stop, on his extortionate terms, to get at its rare earths. He wants Greenland for similar reasons and casts a greedy eye on Canada's resources too. He and the people around him also hate the EU passionately, because they see it as an economic rival built on a very different social model from the devil-take-the-hindmost one they like to promote - a model which, by the way, is very convenient for billionaire tech-bros. For the benefit of its citizens, the EU regulates business, including social media and data gathering on the population by US internet giants. So the EU must fail. Empowering Russia to attack its eastern borders is therefore to be welcomed. These ideas are far easier to implement if domestic opposition is neutralised. After all, they represents the overturning, not only of 80 years of US foreign policy but the basic ideals of respect, fairness and morality that go with upholding the rule of law and respecting national borders. At home, the soft coup is now well in progress, with Congress neutralised, the courts ignored, the media cowed and state employees subjected to a Stalinist terror by Musk. DOGE is sacking vast numbers of them arbitrarily and furthermore encouraging them to inform on one another, as a means of sowing internal suspicion and destroying any attempt to resist. The stated goal in Project 2025 is to replace those sacked with those loyal to The Leader, the first interview question no doubt being, "Do you agree the 2020 election result was stolen by Biden?"

Yeah and now, with $$$ signs in his eyes, Trump is actually accusing Zelensky, a man who has out-Churchilled Churchill for his country, of being a dictator! WTF?

A useful word, which was adopted some years ago in our household to refer to decaffeinated coffee, to distinguish it from the unadulterated version.

Thanks for these further references. I too had stumbled across Haüyne . This mineralogists' discussion about nomenclature was interesting. Whatever the ins and out of the naming of these minerals, it seems clear than when they are bright blue it is due to polysulphide anions in the cages, replacing a proportion of what would otherwise have been sulphate. Chivers comments in his paper that in earlier work people thought the anion was S₂⁻ (your scanned pages reflect this earlier view) but it is now recognised to be this S₃•⁻, with the odd electron in the π* antibonding orbital, that is responsible for the absorbance that creates the colour. Pyrite is indeed found in association with lapis lazuli but my suspicion, from the Chivers paper about the reversible formation of S₃•⁻ in the lab at elevated temperature and pressure, is that the same hydrothermal fluids that create pyrite can also alter suitable rocks to create lapis lazuli, by partial replacement of sulphate with this trisulphide radical anion. Anyway, all good and interesting stuff. I must pop back to the Natural History museum for another interesting mineral. There were some very dramatic, long, blackish crystals of stibnite, for example.......

Hmm, but all you are saying is that we don’t as yet have a model for the process. That’s what makes it an object of study, of course. Wondering about reproducibility in the lab is the sort of thing only someone with little understanding of the science would do. As a “question to ask”, it is very naïve - or disingenuous, but in your case I’ll assume naïvety, pro tem. The biochemistry of a living organism is very complex indeed. There is no reason to expect that assembly of all the components required, in a functional form, could be accomplished in a lab on a human timescale. Other contributors to the thread have already made this point.

But how is this any different from us not being to observe directly geological processes, say, or the formation of stars? There are many aspects of science that depend on inference of a process from observations, without being able to observe the process directly. Do you think the origin of life is unique in this respect, for some reason? If so, what?