The Big Idea Behind Avogadro's Number (That Most People Miss)

This video steps backward to begin the story of Avogadro's number back in ancient Greece, similarly to how I teach the atomic history in my chemistry class at Princeton.

The development of relative masses of the elements, though, is something that I tend to skim over fairly quickly, though I might start putting a bit more emphasis on this concept in the past.

I do, however, mention - partially thanks to Steve Mould's explanation of moles - define the moles as the conversion factor between one gram and one atomic mass unit. 

I didn't know, however, that the value for Secret Number N was discovered in 1909. Now I guess I need to find out how that value was discovered more than 100 years ago.