On the periodic table, helium has the lowest boiling point of any element.
Helium boils at about 4.22 kelvins, or −268.93 °C, at standard atmospheric pressure. Its atoms interact only very weakly, so unusually little thermal energy is needed to keep them from condensing into a liquid.
Helium is the second element, with atomic number 2, and belongs to the noble gases. It is chemically inert under ordinary conditions because its first electron shell is full. Helium is unusual among elements because it does not solidify at normal pressure, even at absolute zero; pressure is required to make solid helium.
The element was first identified in the Sun’s spectrum during the 1868 solar eclipse, before it was found on Earth. Its name comes from Helios, the Greek god of the Sun. Liquid helium is valuable for cryogenic cooling, including superconducting magnets in medical imaging systems.