Helium
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Helium is a chemical element. It has the chemical symbol He and atomic number 2.
Helium is called a noble gas, because it does not regularly mix with other chemicals and form new compounds. It has the lowest boiling point of all the elements. It is the second most common element in the universe, after hydrogen, and has no color or smell. Helium does not usually react with anything else. However, it can react with tungsten, iodine, fluorine, sulfur and phosphorus under very special conditions.
Pierre Janssen and Norman Lockyer found helium in 1868. They found that it was in the Sun before it was found on Earth. Because of where it was found, its name comes from the Greek word for Sun, helios.
It is used to fill balloons and airships because it is lighter than air, and does not burn or react, meaning it is normally safe for using it in that way. It is also used in some kinds of light bulbs. People also breathe it in to make their voices sound higher than they normally do as a joke, but this is extremely dangerous, and should not be done, since it can kill them, since they are not breathing normal air.