Search the Properties of Matter site Properties of Matter glossary Photos, illustrations and streaming media on the Properties of Matter site Properties of Matter table of contents Properties of Matter home page Link to NSRC home page

Properties of Matter Element Card, Lesson 21



Melting point

-272° C

Boiling point

-269° C


0.00018 g/cm³


Helium is colorless.

Other physical properties

Helium is the second least dense element.

Chemical properties

Helium is odorless and does not react easily with other elements.




Helium is used to inflate weather and party balloons as well as modern airships and blimps. It is mixed with oxygen for use by divers.


Helium is the second most abundant gas in the universe. It was discovered in the sun by a technique known as spectroscopy before it was found on Earth. It gets its name from Helios, the god of the sun in Greek mythology.

A man standing on a balcony holding the rope to a large silver weather balloon

Only hydrogen is less dense than helium. Helium is used to fill balloons, such as this NASA research balloon. Why is helium used for this purpose instead of hydrogen?

a scuba diver underwater

Helium/oxygen mixtures are used by divers who descend to great depths. When breathed under pressure, helium has less toxic effects than nitrogen, the major component of air. When nitrogen is breathed under pressure, it can cause nitrogen narcosis, a condition that can disorient divers.

Information about the STC/MS curriculum Link to NSRC home page NSRC contact information NSRC copyright and permissions information Smithsonian Institution privacy policy Properties of Matter site map