Helium is the first member of the noble gas family, the elements that make up Group 18 of the periodic table. Its atomic number is 2, its atomic mass is 4.002602, and its chemical symbol is He.

Properties

Helium is a colorless, odorless, tasteless gas with a number of unusual properties. For example, it has the lowest boiling point of any element, -452°F (-268.9°C). Its freezing point is -458°F (-272.2°C). At a temperature of about -456°F (-271°C), helium undergoes a striking change. It remains a liquid, but a liquid with unusual properties. One of the most interesting of those properties is superfluidity, a condition in which a liquid flows upwards out of a container against the force of gravity and may pass through very small holes that would normally be impermeable to the gas. Chemically, helium is completely inert...