How many atoms is in, Asprin, pain reliever, 3C9H8O4?

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

How is the atomic number of a nucleus changed by alpha decay