Lowest melting point of any element

Helium (symbol He, atomic weight 2) is the second lightest element known after Hydrogen. Discovered in 1868 by French astronomer Pierre Janssen while observing spectral lines during a solar eclipse, Helium is inert, colourless and odourless, as well as possessing the unique property of remaining liquid at Absolute Zero (0K) at atmospheric pressure. This is the direct result of quantum mechanics in which the zero-point energy (the lowest possible energy a physical system may have) is still enough to prevent freezing. Only by applying 25 bar (2.5 MPa) pressure at temperatures of between 1 to 1.5K will solid helium form. Even solid helium is ununsual in that it 'looks' very much like liquid helium and can be compressed to 60% of its normal solid volume (~100 times more compressible than water). Liquid helium below 2.1768K is known as Helium II and is a true superfluid with no measureable viscosity. Most of the helium produced today is found in a small number of North Americian natural gas wells.