How many atoms would measure 1 millimetre across?

Answer 1

Well, honey, if we're talking about a millimeter, which is one thousandth of a meter, and an atom is about 0.1 nanometers in size, then you'd be looking at roughly 10 million atoms across a millimeter. But hey, who's counting?

Answer 2

That depends on the element and atom you use, and even the definition of size/atomic radius. Using hydrogen atoms at a radius of 25 picometres, you could fit 40000 000000 (forty trillion) of them in a straight line across one milimetre.