IN A NUTSHELL:

Little Mix are at a prom.

There are balloons filled with helium.

Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.

Helium is the second lightest element and is the second most abundant element in the observ­able universe, being present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this figure in the Sun and in Jupiter. This is due to the very high nuclear binding energy (per nucleon) of helium-4 with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radio­act­ive decay. Most helium in the universe is helium-4, and is believed to have been formed during the Big Bang. Large amounts of new helium are being created by nuclear fusion of hydrogen in stars.

Helium is named for the Greek god of the Sun, Helios. It was first detected as an unknown yellow spectral line signature in sunlight during a solar eclipse in 1868 by French astro­nomer Jules Janssen. Janssen is jointly credited with detecting the element along with Norman Lockyer. Jannsen observed during the solar eclipse of 1868 while Lockyer observed from Britain. Lockyer was the first to propose that the line was due to a new element, which he named. The formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, who found helium emanating from the uranium ore cleveite. In 1903, large reserves of helium were found in natural gas fields in parts of the United States, which is by far the largest supplier of the gas today.

Liquid helium is used in cryo­gen­ics (its largest single use, absorbing about a quarter of pro­duc­tion), par­tic­u­larly in the cooling of super­con­duct­ing magnets, with the main com­mer­cial applic­a­tion being in MRI scanners. Helium's other indus­trial uses—as a pres­sur­iz­ing and purge gas, as a pro­tect­ive atmo­sphere for arc welding and in processes such as growing crystals to make silicon wafers—account for half of the gas produced. A well-known but minor use is as a lifting gas in balloons and airships.[4] As with any gas whose density differs from that of air, inhaling a small volume of helium tem­por­ar­ily changes the timbre and quality of the human voice. In sci­entific research, the behavior of the two fluid phases of helium-4 (helium I and helium II) is important to research­ers studying quantum mechanics (in par­tic­u­lar the property of super­fluid­ity) and to those looking at the phenomena, such as super­con­duct­iv­ity, produced in matter near absolute zero.

On Earth it is rel­at­ively rare — 5.2 ppm by volume in the atmo­sphere. Most ter­restrial helium present today is created by the natural radio­act­ive decay of heavy radio­act­ive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei. This radio­genic helium is trapped with natural gas in con­cen­tra­tions up to 7% by volume, from which it is extracted com­mer­cially by a low-tem­per­at­ure sep­ar­a­tion process called frac­tional dis­til­la­tion. Helium is a finite resource, and once released into the atmo­sphere, it readily escapes into space.