The hydrogen atom is the smallest that we know and it has a very simple structure: one proton with a positive charge and one electron with a negative charge.

Hydrogen occurs as a gas that you can’t see and can’t smell. It is about 14 times lighter than air. When you combine two atoms of hydrogen with one atom of oxygen you get a water molecule H2O. Like nitrogen, hydrogen can also be condensed to a liquid that freezes at – 259°C (-434°F) and boils at -252°C (-423°F).

Hydrogen is one of the most common elements in our universe. The sun and many stars are made of hydrogen. It can also be found in the Earth’s crust. Hydrogen is in many compounds of animals and plants.

Hydrocarbons are compounds that only have hydrogen and carbon in them, like petroleum, natural gas or plastic.

Hydrogen has many uses. When two hydrogen atoms get together, they form a molecule and give off a lot of heat. That’s why, together with oxygen, hydrogen makes a good fuel. It, for example, powers the engines of space rockets. Power plants use hydrogen to produce energy. There are even cars that run on hydrogen fuel. When you add hydrogen to coal, you can make petrol.

Rockets burn liquid hydrogen and oxygen to lift off
Image: NASA, Public domain,
via Wikimedia Commons