The most common element in the universe is hydrogen. It makes up about 75% of the universe's elemental mass and is the simplest and lightest element, consisting of just one proton and one electron
. Hydrogen was formed shortly after the Big Bang during the process of Big Bang nucleosynthesis and serves as the primary building block of stars, fueling nuclear fusion that converts hydrogen into helium and releases vast amounts of energy
. Helium is the second most abundant element, and together hydrogen and helium constitute over 98-99% of the known matter in the universe
. Other elements like oxygen, carbon, neon, nitrogen, and iron are much less abundant by comparison, making up only a small fraction of the universe's elemental composition
. In summary:
- Most abundant element: Hydrogen (~75% of elemental mass)
- Second most abundant: Helium
- Combined abundance of H and He: Over 98-99% of the universe's matter
- Other elements: Much less common, with oxygen being the third most abundant
