I was looking on the [Wikipedia page](https://en.m.wikipedia.org/wiki/SI_base_unit) for all of the base SI units, and was surprised to see that mole was considered a base unit.
Why is this even a unit? Shouldn’t it be a unit-less quantity? A mole isn’t length, or time, or mass, it’s just a number. Why does it need a unit if it just represents “6×10²³ of something”?
You don’t need units to say “I have 15 pencils,” so why is the mole necessary? It seems like a mole is just a scalar.
In: 10
One can interpret a mole as a scalar, but that is somewhat missing the point. Scalars can be multiplied; amounts of things can not. What is 3 pencils times 4 pencils? It isn’t 12 pencils, it is 12 of the very weird abstract “pencils squared”. But you can multiply 12345 molecules by the abstract scalar number 7 and get again a count of molecules. Same works identically with 3 moles (which is just a lot more molecules than 12345).
The basic SI units form, well, a basis: any mass, any length, any time interval, …, and any amount of particles can be expressed a multiples of them. There is no reason to pick 1 over the mole as the fundamental counting unit, each has advantages and disadvantages. The reason we decided on the latter is that it is in the range of everyday objects and amounts chemistry usually deals with. We could pick one instead, and see mole as a constant like c, G and such; but why having one more constant instead of a unit? It is all choice.
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