What is the quantum mechanical approach of explaining the fact that:
"The size of the atom increases when a new shell is filled" ??? I mean how do you explain this phenomenon using ideas of quantum mechanics....besides classical ideas...???
Discussions in comments below How can aerogel be lighter than air? really make an answer to this important. The conclusions there are that aerogel could in some cases be "lighter than air" if one takes only the mass of the aerogel material and ignores the mass of any trapped gas within each cell,...