Helium Helium Helium (from ) is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements. After hydrogen, helium is the second lightest and second most abundant element in the observable universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter. This
Critical points of the elements (data page) Critical points of the elements (data page) David R. Lide (ed), "CRC Handbook of Chemistry and Physics, 85th Edition", online version. CRC Press. Boca Raton, Florida, 2003; Section 6, Fluid Properties; Critical Constants. Also agrees with Celsius values from Section 4: Properties of the Elements and Inorganic Compounds, Melting, Boiling, Triple, and Critical Point Temperatures of the Elements J.A. Dean (ed), "Lange's Handbook of Chemistry" (15th Edition), McGraw-Hill, 1999; Section 6; Table 6.5 Critical Properties National Physical Laboratory, "Kaye and Laby Tables of Physical and Chemical Constants"; D. Ambrose, M.B. Ewing, M.L. McGlashan, Critical constants and second virial coefficients of