What is the most abundant element in the universe?
Hydrogen is the most abundant element in the universe. It makes up about 74 percent of all normal matter by mass, and helium makes up most of the rest.
Hydrogen and helium formed in the first few minutes after the Big Bang, about 13.8 billion years ago. The universe was then so hot and dense that protons and neutrons could fuse only into these light elements and small amounts of lithium.
Heavier elements, such as carbon, oxygen and iron, were made much later inside stars. When massive stars explode as supernovas, they scatter these elements into space, where they become part of new stars, planets and living things. Even so, all the heavier elements together make up only about 2 percent of normal matter.
On Earth it is different
Earth's crust is mostly oxygen and silicon, and the whole planet is mostly iron, oxygen, silicon and magnesium. Light hydrogen and helium gas escaped from the young Earth, but hydrogen survives here in water and in the molecules of living things.
Did You Know?
Normal matter, made of atoms, is only about 5 percent of the universe. The rest is thought to be dark matter and dark energy, which scientists are still trying to understand.