Helium is an element of the periodic table that is composed of subatomic particles including protons, neutrons and electrons. The atomic number of helium is 2, which means it contains two protons and two electrons. The most common isotope of helium contains two neutrons.
Helium is designated by the chemical symbol He and is the lightest of the noble gases. Like the other noble gases, helium is nonreactive. It has the lowest boiling and melting points of all the elements.
Helium is the second most abundant element in the universe after hydrogen, but it is rare on Earth. Most of the helium used in industry comes from natural gas, and the majority of the Earth's helium supply is extracted from wells in Texas, Oklahoma and Kansas.