Will scientists ever find smaller elements or is hydrogen the smallest possible?
The number of protons in an atom's nucleus determines which element it is. To make an element simpler than hydrogen, one would have to remove a proton from hydrogen's nucleus. This is a problem since an atom of hydrogen only contains one proton to begin with. Remove that proton and you no longer have an atom. Hydrogen, which contains a single proton in its nucleus, is the simplest element.
Steve Gagnon, Science Education Specialist (Other answers by Steve Gagnon)