system
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human
How were the number of atoms in a mole determined?

I'm trying to do a bit of reading on this and what I've read so far doesn't seem to get at it. I get the definition of there being 6.02x10^23 atoms in 12 grams of carbon 12, but how did they 'count' the atoms in those 12 grams?
gpt
First, a bit if history. Avogadro had made the idea of a mole as you described (12 grams of carbon in carbon 12), but he didn't actually create the constant of 6.02x10^23. What's important is that moles have been around.

Michael Faraday worked in the 1830s on electrolysis, and he had been able to calculate the electric charge per mole of electron. The number of elections was still not known, though.

In 1910, Robert Millikan was able to measure the charge of an election. Taking something like hydrogen, for example, he had to get a mole of hydrogen which was a mass he already knew, calculate the charge, and divide that by the charge of one electron. That formula gave him the number of electrons, and the constant we use today.