Helium
Beginning of paper
, 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
eclipse in 1868.
Helium is the lightes ....
Middle of paper
.... to
absolute zero. Liquid helium can be cooled 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 isot ....
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