Hélio

In Portuguese, hélio is the name for the chemical element helium. Helium is the second-lightest element in the periodic table and the least reactive of the noble gases. It is colorless, odorless, and non-toxic, and it remains a gas at most common temperatures and pressures. It has the chemical symbol He and an atomic number of 2.

The name derives from the Greek helios meaning sun, reflecting early identification in the solar spectrum. Helium was first observed in the Sun’s spectrum in 1868 by Pierre Janssen and Norman Lockyer, and was later isolated on Earth in 1895 by William Ramsay and Morris Travers during the processing of liquefied air.

In Earth's atmosphere, helium is rare, comprising about 5 parts per million by volume. It is extracted from natural gas deposits and through the fractional distillation of air. Helium is notable for its extremely low boiling point, around 4 kelvin, which makes it essential for cooling superconducting magnets in MRI scanners, research accelerators, and other cryogenic applications. It is also used to fill balloons and some leak-testing procedures due to its low density and inertness.

As an inert gas, helium does not react with most substances. However, it can pose asphyxiation risks if it displaces air in enclosed spaces. Safety measures include proper ventilation and handling to prevent oxygen depletion. Helium has two stable isotopes: helium-3 and helium-4, with helium-4 by far the most abundant on Earth.