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Helium - A Beginners' Guide

Helium is a colourless, odourless gas at room temperature (298 K). It is the lightest of all of the noble gases and is virtually chemically inert; as such, helium is used in lighter-than-air balloons from party balloons to huge airships.It also has significant industrial and technological uses, particularly as a refrigerant, including for magnetic resonance imaging (MRI) in many hospitals, and in many industrial processes.

Despite being the second most abundant element in the universe (after hydrogen), helium is very rare on Earth as most of the helium gas which was present during the formation of the Earth was subsequently lost as helium is light enough to escape the Earth's gravitational pull. There is now serious concern over the continued availability of helium so it is important that the gas is conserved where possible.

Helium was unknown on Earth until 1868 when Pierre Janssen, a French astronomer, decided to measure the spectrum of the chromosphere of the Sun. Janssen's spectrum showed a bright emission line in the yellow part of the spectrum that could not be experimentally repeated in the laboratory. Norman Lockyer, an English astronomer, realised that this emission line must be due to some currently unknown element, which he dubbed 'helium' after the Greek sun god Helios.

The helium we use today is a product of natural radioactive decay; due to it's lighter than air nature, significant quantities of helium only occur where the gaseous decay products can accumulate over a significantly long period of time. As such, the majority of the helium found on Earth is mixed in with other natural gases trapped deep beneath the surface in gas wells.