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Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures.Liquid helium may show superfluidity.. At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temperature of −269 °C (−452.20 °F; 4.15 K).
Pure-play helium, also known as primary helium or green helium is helium that is extracted from the earth as the main product. Since the early 20th century, most of the world's helium supply has been extracted from natural gas as part of the nitrogen rejection process. The preference for primary helium is driven by the planned reduction in use ...
Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. [1] Helium's first ionization energy of 24.57 eV is the highest of any element. [2]
The symbol 4.1 H (Hydrogen-4.1) has been used to describe the exotic atom muonic helium (4 He-μ), which is like helium-4 in having two protons and two neutrons. [5] However one of its electrons is replaced by a muon, which also has charge –1.
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Helium is a commonly used carrier gas for gas chromatography. The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating. [28] [30] Helium at low temperatures is used in cryogenics and in certain cryogenic applications.
At ambient pressure the boiling point of liquefied helium is 4.22 K (−268.93 °C). Below 2.17 K liquid 4 He becomes a superfluid ( Nobel Prize 1978, Pyotr Kapitsa ) and shows characteristic properties such as heat conduction through second sound , zero viscosity and the fountain effect among others.
Helium II will "creep" along surfaces in order to find its own level – after a short while, the levels in the two containers will equalize. The Rollin film also covers the interior of the larger container; if it were not sealed, the helium II would creep out and escape. The liquid helium is in the superfluid phase.