What is the lightest element?
Hydrogen is the lightest element. It has just one proton and usually no neutrons, and it is also the most abundant element in the universe.
Hydrogen sits at number 1 on the periodic table. A normal hydrogen atom has one proton in its nucleus and one electron around it. Hydrogen gas is about 14 times lighter than air, which is why early airships were filled with it.
Hydrogen makes up about three-quarters of all normal matter in the universe by mass. Stars, including the Sun, shine by fusing hydrogen into helium deep in their cores. On Earth, most hydrogen is bound up in water and in the organic molecules of living things.
A dangerous lifting gas
Hydrogen burns easily. After the airship Hindenburg caught fire in 1937, hydrogen was largely replaced by helium, the second-lightest element, which does not burn. Today hydrogen is studied as a clean fuel, because burning it or using it in a fuel cell produces only water.
Did You Know?
The English chemist Henry Cavendish identified hydrogen as a separate substance in 1766. The name, given later by Antoine Lavoisier, means water-former.