Periodic Table of the Elements: Helium

Name: Helium
Symbol: He
Atomic Number: 2
Atomic Mass: 4.0026
Atomic Volume: 19.43 cc/mol
Discovered By: Janssen, Ramsay
Discovery Date: First detected in the spectrum of the sun by Janssen during a solar eclipse in 1868. It was isolated by Ramsay in 1895.
Origin of Name: Helium - (Greek) Helios (Sun)
Toxicity: Not toxic. Has narcotic effect at very high pressure (103 kN/m 2 ).
Summary: Helium is an inert gas. It is lighter than air, but somewhat heavier than hydrogen. One cu. ft. of He will lift 0.0685 lb. (0.0311 Kg) at 0° C and 1 atm. Helium does not exist in the solid form at 1 atm pressure; it remains liquid to 0°K. It can be solidified only at higher pressures. One form of liquid helium is a superfluid and has almost zero viscosity. It will flow up and out of a beaker containing it. Most of the atmospheric He has floated out into space. However, He is obtained commercially from natural gas wells.

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