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Why are moles written with 'mol' as opposed to something which is easier to write with one character, or even two?

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    $\begingroup$ Cuz "m" is for meters and "mo" sounds kinda silly. $\endgroup$ – Ivan Neretin Oct 12 '20 at 16:51
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    $\begingroup$ There are other alphabets and it doesn't necessarily have to resemble the word 'mole'; for example the unit for distance isn't 'd' $\endgroup$ – yolo Oct 12 '20 at 17:01
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    $\begingroup$ It can be of interest to some of the readers and OP. And it is not up to date. Indeed I am not ashamed to say that I still have to digest the latter changes in the International System. Perhaps one of us can Ask & Answer about the impact of the recent units definition to the Periodic Tables hanging in our room / office / lab, if any. Beside that, here is the link degruyter.com/configurable/contentpage/… $\endgroup$ – Alchimista Oct 12 '20 at 18:31
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    $\begingroup$ @Karl Now ?? The mole was made the seventh SI base unit in 1971 by the 14th CGPM. Its definition was just updated recently. $\endgroup$ – Poutnik Oct 13 '20 at 7:36
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    $\begingroup$ @ Yolo. You say that the unit for distance is not $d$, and you are right. The unit for distance is "meter", with an abbreviation $m$. In the same direction, the unit for chemical amount is not "chem something". It is "mole", and it has an abbreviation $mol$. $\endgroup$ – Maurice Oct 13 '20 at 9:45
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The symbol mol is due to Ostwald who was a very influential and respected physical chemist more than a century ago. In German, "mole" is "Mol". It is a shortform of Molekül.

I believe the Internet Archive has an English translation of his historically famous book of 19th century. This is where I recall reading this. The original reference is W. Ostwald Hand- und Hilfsbuch zur Ausführung physikochemischer Messungen. This book is available on Google Books (pg 278). A footnote appears there:

Um nicht stets den schleppenden Ausdruck Gramm -Molekulargewicht brauchen zu müssen, werde ich diese Größe in der Folge kurzweg Mol nennen, und erlaube mir, diesen Vorschlag zur allgemeinen Annahme zu empfehlen. Man schreibt ohnedies diese Größe häufig Mol., und braucht daher nur den Punkt fortzulassen.

In order not to always have to use the sluggish expression gram - molecular weight, I will simply call this quantity Mol in the following, and allow me to recommend this proposal for general acceptance. Anyway, this quantity is often written as Mol., so you only have to omit the point.

Translated via (www.deepl.com) with some manual changes.

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The mole was promoted to the status of "unit" in 1971

The 14th Conférence Générale des Poids et Mesures (CGPM),

considering the advice of the International Union of Pure and Applied Physics, of the International Union of Pure and Applied Chemistry, and of the International Organization for Standardization, concerning the need to define a unit of amount of substance,

decides

  1. The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol".
  2. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
  3. The mole is a base unit of the Système International d'Unités.

It had been in use before that for quite some time, and I guess nobody wanted to change the symbol. Think about the ensuing confusion if you made up a new unit symbol today, that means exactly the same thing as the old one.

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    $\begingroup$ The mole unit ( symbol mol , like kilogram has the symbol kg ) is not only ordinary SI unit, but 1 of 7 base SI units since 1971. $\endgroup$ – Poutnik Oct 13 '20 at 8:18
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    $\begingroup$ @Poutnik In the grand scheme of the cosmos, this is fairly recent though. ;) $\endgroup$ – Martin - マーチン Oct 13 '20 at 10:41
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    $\begingroup$ @Martin-マーチン Like the whole science, isn't it ? :) $\endgroup$ – Poutnik Oct 13 '20 at 10:42
  • $\begingroup$ @Poutnik I looked it up now, and you're right of course. I distinctly remember my school teachers calling it "sort of" a unit, reasoning that it is mostly just a unitless number. And I'm sure most of my teachers had gotten their university degrees after 1971. ;-) $\endgroup$ – Karl Oct 13 '20 at 18:01
  • $\begingroup$ You may know as of 2019 some S.I base units have been redefined [en.wikipedia.org/wiki/… if you are interested then go through this. $\endgroup$ – user99496 Oct 15 '20 at 6:03

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