Comment by adrian_b | Hacker News Reader

Comment by adrian_b | Hacker News Reader

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What you say proves that this was not an AI post, because all the AIs are trained on erroneous sources, where bismuth is called "metal" (the older better chemistry manuals may either be not scanned or available only in some archiving sites).

Even if useful definitions for the terms "metal" and "semi-metal" are 300 years old, as I have said, many modern manuals either do not give any proper definition for the term "metal", or even if they do they do not follow it consistently, so sometimes they apply the word "metal" to substances like bismuth, whose only resemblance to a metal is having free electrons. If this rule were followed consistently, graphite would also have to be named "metal", but no manual does that.

While having free electrons may be the most important property of metals for electrical and electronics engineering, for mechanical engineering and for manufacturing any kind of devices, the other property of metals, ductility, is far more important. This is why the distinction between ductile metals and intrinsically fragile semi-metals is very important.

In this case, the use of the word "metal" for bismuth is a clear cause of confusion, as it suggests an aromatic ring made of electro-positive atoms, which would be a real surprise. An aromatic ring made of atoms with the electro-negativity of bismuth is no surprise.

The elements with high electro-negativity, which in elemental form are semi-metals, semiconductors or non-metals, form covalent bonds between their atoms.

The elements with low electro-negativity, which in elemental form are true metals, form metallic bonds between their atoms.

So the expected chemical behavior for "metals" and for "semi-metals" is quite different.

This entire comment is, i am sorry to say, silly. ou are arguing that the element bismuth should be called a "semimetal" as opposed to a "metal", and in a sense, you are correct.

in another sense, however, it would also make sense to call it and every other element heavier than helium "metal"; since that is how things are done in astronomy, where the arguably most important elements are the first ones.

But when one reads "metal" without any other context, one generally interprets the term within the context of chemistry, where bismuth is absolutely referred to as a "metal", a "post-transition metal" to be more precise.

That is to say, you are the botanist showing up and calling the tomato a fruit, wheras the rest of the world understandably calls it a vegetable.

Nit: Things above helium are called metals. Helium is not.

Another nit: Astronomy, not astrology.

Ah, that was quite an embarrasing error on my part, thanks.

One can choose to classify the chemical elements with whatever words one pleases.

Nevertheless, some classifications are much more useful than others.

A classification that no longer uses the traditional distinction between metals and semi-metals is much less useful than a classification that distinguishes these 2 categories. Neglecting this distinction demonstrates a lack of understanding about which are the properties that determine the usefulness for practical applications of the chemical substances and a lack of understanding of how such properties vary with the atomic number.

Moreover, after one chooses some classification rules, those must be followed consistently. For example, anyone who chooses to call bismuth as a "metal" must also call carbon as a "metal", because the most stable state of carbon in normal conditions, i.e. graphite, has exactly as much reasons to be named as a "metal" or as a "post-transition metal" as bismuth has. There are a very large number of chemical compounds that are semi-metals, but among the pure elements carbon, antimony and bismuth are semi-metals (while boron, silicon, germanium, selenium and tellurium are semiconductors).

The reality is that too many authors of manuals just copy and paste automatically texts from other works without stopping to think whether they are correct and consistent.

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