Which element has the lowest boiling point?

Helium is the element with the lowest boiling point, boiling at about 4.222 kelvins, or −268.928 °C, at standard pressure. Its boiling point is lower than that of every other element, including hydrogen, the lightest element.

Helium’s exceptionally low boiling point comes from its weak interatomic attractions and very low atomic mass. It is a noble gas, so its atoms are chemically inert and exist as separate, monatomic particles. Helium is also unusual because at ordinary atmospheric pressure it does not freeze, even near absolute zero; pressure is required to make solid helium.

Below about 2.17 K, liquid helium-4 becomes helium II, a superfluid that can flow with virtually no viscosity through extremely narrow spaces. Helium was first identified in the Sun’s spectrum in 1868 and later isolated on Earth in 1895. Its low boiling point makes it valuable for cooling superconducting magnets in MRI scanners and other cryogenic equipment.