Beginning of Essay
, symbol He, inert, colorless, odorless gaseous element. In group 18 (or VIIIa) of the periodic table, is one of the noble gases. The atomic number of is 2. The French astronomer Pierre Janssen discovered in the spectrum of the corona of the sun during an ecli ....

Middle of Essay
.... almost to absolute zero at normal pressure by rapid removal of the vapor above the liquid. At a temperature slightly above absolute zero, it is transformed into helium II, also called super fluid helium, a liquid with unique physical properties. It has no freezing point, and its viscosity is zero; it passes readily through minute cracks and pores and will even creep up the sides and over the lip of a container. Helium-3, the lighter helium isotope of mass 3, which has an even lower boiling point than ordinary helium, exhibits markedly different properties when liquefied. Because it is noncombustible, helium is preferred to hydrogen as the lif ....