What is the most abundant element in the universe?
Quick answer
Hydrogen is the most abundant element in the universe, making up about 74% of all normal matter by mass and about 90% of all atoms. Helium is second at about 24%. Everything else, including the oxygen, carbon and iron that make planets and people, adds up to only about 2%.
The most abundant elements in the universe
| Rank | Element | Share by mass (approx.) |
|---|---|---|
| 1 | Hydrogen | ~74% |
| 2 | Helium | ~24% |
| 3 | Oxygen | ~1% |
| 4 | Carbon | ~0.5% |
| 5 | Neon | ~0.13% |
| 6 | Iron | ~0.11% |
Why so much hydrogen?
Hydrogen is the simplest element, with just one proton and one electron. It formed in the first few minutes after the Big Bang, along with most of the universe’s helium. Heavier elements were made much later, inside stars, which fuse hydrogen into helium and then build heavier atoms. That’s why astronomers say we’re made of “star stuff.”
The answer changes depending on where you look
| Place | Most abundant element |
|---|---|
| Universe | Hydrogen |
| Sun | Hydrogen (~73% by mass) |
| Earth’s crust | Oxygen (~46%) |
| Earth as a whole | Iron (mostly in the core) |
| Earth’s atmosphere | Nitrogen |
| Human body | Oxygen by mass; hydrogen by number of atoms |
Where hydrogen is found on Earth
Most of Earth’s hydrogen is locked in water (H₂O). Hydrogen gas is very light and escapes into space easily, so there’s very little free hydrogen in our air.
Hydrogen today
- Fuel: Hydrogen fuel cells produce electricity with water as the only exhaust.
- Industry: It’s used to make ammonia for fertilizers.
- History: The Hindenburg airship was filled with flammable hydrogen when it burned in 1937; modern blimps use helium.
The Sun shines by fusing hydrogen; see how hot the Sun is. Jupiter, the largest planet, is also mostly hydrogen: what is the largest planet.
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