Helium (He), chemical element, inert gas of Group 18 (noble gases) of the periodic table. The second lightest element (only hydrogen is lighter), helium is a colourless, odourless, and tasteless gas that becomes liquid at −268.9 °C (−452 °F). The boiling and freezing points of helium are lower than those of any other known substance. Helium is the only element that cannot be solidified by sufficient cooling at normal atmospheric pressure; it is necessary to apply pressure of 25 atmospheres at a temperature of 1 K (−272 °C, or −458 °F) to convert it to its solid form. Continue reading from Encyclopedia Britannica
On Aug. 18, 1868, a total eclipse obscured the sun. French astronomer Pierre Janssen was on-hand in India to watch, and to measure the sun's atmosphere, known as the chromosphere. In the spectrum of gases he observed in the chromosphere was a strange yellow line with a wavelength of 587.49 nanometers, according to the Jefferson Lab.
Janssen didn't identify the source of this wavelength. Two months later, though, English astronomer Sir Norman Lockyer set up his own spectroscope in London and saw that same yellow line. Working with chemist Edward Frankland, Lockyer concluded that the line was the fingerprint of an unknown element. The scientists dubbed this mystery element "helium," after Helios, the Greek god of the sun.
The discovery of helium on Earth took longer. According to the Royal Society of Chemistry, Italian physicist Luigi Palmieri observed a wavelength of 587.49 nanometers in gases emitted from Mount Vesuvius in 1882, the first detection of helium on Earth. It wasn't until 1895, however, that helium's presence on Earth was confirmed and that scientist discovered its atomic weight. Credit for this discovery goes to Swedish chemists Per Teodor Cleve and Nils Abraham Langer. Continue reading from LiveScience
The Federal Helium Reserve, operated by the U.S. Bureau of Land Management, is near Amarillo, Texas. It holds over 40 percent of the helium used annually in the United States. Helium on Earth is formed when radioactive elements in the crust decay, producing positively charged particles called alpha particles. When these alpha particles attract a couple of electrons, the result is a helium atom. No one has ever successfully made helium combine with another element to create a compound, according to the Jefferson Lab. It's just that inert. Continue reading from LiveScience
