The air around us on Earth is a mixture of gases. You can’t see them because they don’t have a colour and you can’t smell them, either.
Nitrogen makes up more than three-quarters of the air around us (about 78%). It has the chemical symbol N in the periodic table. Nitrogen has lots of uses: for example, we can use it to keep food fresh. Did you know that nitrogen is the gas inside a crisp packet?!
Oxygen (chemical symbol O) makes up about one-fifth (21%) of air. When we breathe, some of the oxygen from the air passes through our lungs into our blood. Oxygen is very important because our bodies use it in chemical reactions to make the energy we need to stay alive.
Argon (chemical symbol Ar) makes up less than 1% of air. It is used in light bulbs and we put it in the space in between the two panes of glass of double-glazed windows to help keep our houses and other buildings warm.
These three gases add up to nearly 100% of the air around the Earth. But there is also a small amount of carbon dioxide and teeny-tiny amounts of a few other gases.
Carbon dioxide is a compound made up of carbon and oxygen. It has the chemical formula CO2 (which means that each molecule has one carbon atom and two oxygen atoms). Carbon dioxide can be used in fire extinguishers: look for the ones that have black nozzles.
Air also has some water vapour (tiny droplets of water) floating around in it. This comes from the evaporation process in the water cycle. You can see the water vapour when it condenses into clouds.