Name helium
Symbol He
Atomic Weight 4.002602
Atomic Number 2
CAS ID 7440-59-7
Group Number 18
Group Name Noble Gas
Period Number 1
Origin of Name Greek, helios = "sun."
Year Discovered 1895
Discovery Credits Isolated in 1895 by Sir William Ramsay at London, UK, and independently by P. T. Cleve and N. A. Langlet at Uppsala, Sweden.
Class Non-Metallic
Color Colorless
Standard State Gas at 77 F & 298 K
Description Colorless, odorless gas. Unreactive chemically. Used in deep-sea diving, weather balloons, and low temperature research instruments. Most natural sources of helium come from natural gas deposits where He is present from the alpha particle decay of heavy radioisotopes of U and Th and their daughter products.

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