On Wednesday I tried to define a #metamaterial.
Now it's time to define #metals, which should be way easier, right?
Spoiler: even in a #metallurgy group @LNM_eth, not everyone agrees!
Now it's time to define #metals, which should be way easier, right?
Spoiler: even in a #metallurgy group @LNM_eth, not everyone agrees!
https://twitter.com/RealSci_Nano/status/1587733696932679680?s=20&t=uD_atWJY3kTRdNhQo7gg0A
First a list of "high-school science" definitions that don't really help us. The
"Metals are reflective": Yes but not all reflective things are metals. Not definition friendly.
"Metals are reflective": Yes but not all reflective things are metals. Not definition friendly.
"Metals are ductile and malleable, easy to work with": Not necessarily. Good luck working with Tungsten, which is definitely metal.
This article tells a bit about how hard making the Tungsten filaments that we used on lights was!
americanscientist.org/article/tungst…
This article tells a bit about how hard making the Tungsten filaments that we used on lights was!
americanscientist.org/article/tungst…
Until the 19th century, a metal was simply "a dense element". The first known metals were #HeavyMetal after all!
After 1809, light metals like sodium and later aluminium were discovered.
So don't use density as a definition, you are wrong by 2 centuries!
After 1809, light metals like sodium and later aluminium were discovered.
So don't use density as a definition, you are wrong by 2 centuries!
Actually even nowadays different disciplines use different definitions.
Astronomers consider that everything that isn't Hydrogen or Helium is a metal...
So you are all metals! And so is the air that you breathe!
Astronomers consider that everything that isn't Hydrogen or Helium is a metal...
So you are all metals! And so is the air that you breathe!
https://twitter.com/jqfonseca/status/1334261888536948738?s=20&t=O4ai3ZxmMg-guw1UCGZtmA
A pretty popular definition among the #Chemistry community is that metal is a substance whose oxide is basic.
(Basic means something else in chemistry! Basically the opposite of acid. Alkaline is a better word, but alkaline #Memes are boring)
(Basic means something else in chemistry! Basically the opposite of acid. Alkaline is a better word, but alkaline #Memes are boring)
What I call the "bonding definition" seems to be the most popular among material scientists and solid-state physicists: metals are elements held together by metallic bonds aka by the electron cloud.
https://twitter.com/RealSci_Nano/status/1588230715417796609?s=20&t=Rh9WN4TVHDX3afJlByZGpw
The problem with the bonding definition is that it is not too compatible with quantum mechanics: the three kinds of bonds are defined by "where the electrons are", something that QM doesn't allow!
In reality, most bonds are a mixture.
en.wikipedia.org/wiki/Van_Arkel…
In reality, most bonds are a mixture.
en.wikipedia.org/wiki/Van_Arkel…
In #optics, we define #metals as media with negative permittivity.
This requires you to be comfortable with the idea that something might be a metal or not depending on the wavelength.
This requires you to be comfortable with the idea that something might be a metal or not depending on the wavelength.
https://twitter.com/RealSci_Nano/status/1588117079915651072?s=20&t=Rh9WN4TVHDX3afJlByZGpw
So far we have covered what are the wrong definitions of metals (reflective, malleable), what are outdated ones (dense) and which are acceptable as long as you only talk to your immediate-field community.
What is the agreeable definition of metals then?
What is the agreeable definition of metals then?
https://twitter.com/LNM_eth/status/1219264709859381248?s=20&t=Rh9WN4TVHDX3afJlByZGpw
The one that makes the most sense to me and that seems to be accepted by physicists who looked into it is related to electronic conductivity.
"Metals conduct, non-metals don't...at 0K"
pubmed.ncbi.nlm.nih.gov/20123742/
"Metals conduct, non-metals don't...at 0K"
pubmed.ncbi.nlm.nih.gov/20123742/
So only at 0K (-273 C) can we know what a metal actually is.
If you are dissatisfied with the answer, you can extrapolate it and say that in metals the conductivity decreases with temperature, while in other "conductive" solids like semiconductors it is the other way around.
If you are dissatisfied with the answer, you can extrapolate it and say that in metals the conductivity decreases with temperature, while in other "conductive" solids like semiconductors it is the other way around.
However, this extrapolation fails again to describe metals since:
(1) the same happens in electrically conductive liquids.
(2) the case of superconductors needs to be taken into account.
(1) the same happens in electrically conductive liquids.
(2) the case of superconductors needs to be taken into account.
If you made it this far and are disappointed... SORRY! I was too when I found out!
Defining metals is far from trivial, but looking into it is a good #science exercise!
Defining metals is far from trivial, but looking into it is a good #science exercise!
https://twitter.com/RealSci_Nano/status/1588507967766556672?s=20&t=Rh9WN4TVHDX3afJlByZGpw
#SelfPromotion
A blog entry on @MasScience, a Spanish-speaking outreach blog, in which I elaborated on this.
The images were drawn by #design students based on my text, in a #scienceandart project!
masscience.com/2022/06/05/que…
A blog entry on @MasScience, a Spanish-speaking outreach blog, in which I elaborated on this.
The images were drawn by #design students based on my text, in a #scienceandart project!
masscience.com/2022/06/05/que…
• • •
Missing some Tweet in this thread? You can try to
force a refresh
