If there is one thing of which the observable universe has a great deal, it is Hydrogen. Cosmological observations and careful astronomical calculations indicate that about 75 percent of the baryonic (normal) matter (by mass) in the Universe is hydrogen.
One step ahead of the next nine most abundant elements: helium, oxygen, carbon, neon, iron, nitrogen, silicon, magnesium, and sulfur. The mass of all these elements together does not even approach half the amount of hydrogen.
Helium has no gap while we talk about it. Although far from hydrogen, the two elements in the known universe account for an astonishing 99.9 percent of baryonic (normal) matter.