Radon

radioactive element · noble gas · earth science · invisible hazard

Totally invisible and odorless. You cannot see, smell, or taste radon because it's a colorless, odorless gas. Even though it's all around us in the soil and rocks, our senses can't detect it at all.

Radioactive noble gas. Radon is a noble gas, which means it's very stable and doesn't like to react with other elements. It's also radioactive, meaning its atoms are unstable and break apart over time, releasing energy.

Comes from radium decay. Radon is created when radium, another radioactive element deep in rocks and soil, breaks down. This process happens naturally underground and has been going on for billions of years.

Escapes from the ground. Of the different types of radon, only one kind (radon-222) lasts long enough to escape from the soil and seep up into buildings. The other types break down too quickly to make it to the surface.