Which element has the lowest boiling point and melting point?
Helium has the lowest melting and boiling point among all elements. Helium solidifies only under great pressure. Helium fails to solidify and remain a liquid down to absolute zero at normal pressures unlike other elements. Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) and about 25 bar (2.5 MPa) of pressure. The solid has a sharp melting point and has a crystalline structure. Solid Helium is colorless and highly compressible. Liquid helium is also known as “Quantum Fluid”. The viscosity of water is 10000 micropoises, and comparing to this Helium has viscosity of 25 micropoises. In 1926 Williem Keesom was able to solidify Helium by cooling it in a pressure chamber.