Helium

Helium
Properties
Atomic symbol	He
Atomic number	2
Classification	Group 18, Noble gas
Atomic mass	4.0026 amu
Melting point (°C)	-272.2 (26 atm)
Boiling point (°C)	-268.6
Density (grams per cc)	0.1785 (per liter) 0.1380 (relative)
Abundance in lithosphere (%)	5 x 10-4
Other Information
Date of discovery	August 18, 1868
Name of discoverer	Pierre Janssen
Name origin	from Greek mythology: Helios the sun god

Helium is the second element on the periodic table of the elements. It is also the second most abundant element in the universe, after hydrogen. Modern physicists have acertained that most of the helium originated from the Big Bang; however this is disputed by creationists. Both groups generally agree that subsequently helium has been created by nuclear fusion in the center of stars. Helium is also the by-product of alpha-particle radioactivity. Radioactive decay of heavy elements deep inside the Earth sends helium leaking into natural gas wells, from which it is obtained for commercial use. The atomic weight of Helium-4, the most common isotope, is 4.002603254.

The largest supplier of helium in the world is the United States, which produces 44% of the world's total; the U.S. produced 2.15 billion cubic feet of helium in 2020, with 150 times that in recoverable reserves of natural gas.

Helium has an interesting history; during the nineteenth century, one of the things some scientists declared to be "impossible" was the determination of the chemical makeup of the stars. Then spectroscopy was developed, and the composition of the stars became known in great detail. Helium, in particular, was discovered in the Sun (as an unknown element) before it was discovered on the Earth. It was, accordingly, named after Helios, the Greek god of the Sun. It was first found in natural gas in 1905 at the University of Kansas.