iso	NA	half-life	DT	DE (MeV)	DP
³He	0.000137%	He is stable with 1 neutrons.
⁴He	99.999863%	He is stable with 2 neutrons.
⁵He	syn				⁴He
⁶He	syn	806.7ms			⁶Li
⁷He	syn				⁶He
⁸He	syn	119.0ms			⁷Li
⁹He	syn				⁸He
¹⁰He	syn				⁹He

All properties are for STP unless otherwise stated.

Helium is one of the few Noble Gases. There are only six known Noble Gases that are recorded on the Periodic Table of the Elements. Helium is one of the lightest elements on the Periodic Table and is just a little heavier than Hydrogen. It was first discovered in 1895 by Sir William Ramsey though the first evidence of helium was found astronomically in 1868. During a solar eclipse several people noticed a yellow spectrograph line in the corona around the sun which was later found to be caused by the presence of helium. It got its name from the Greek word Helios which means sun. Helium has a mass of 4.002602 g/mol, its Atomic Symbol is He and its Atomic Number is 2.

1 Properties
2 Occurrences
3 Uses
4 Isotopes
5 History of Helium
6 Evidence for a Young Earth
7 Related References
8 See Also

Properties

Helium filled discharge tube shaped like the element's atomic symbol.

Helium is one of the few Noble Gases in the Periodic Table of Elements. It has no color, taste or odor. Even though it is a gas, it can be made into a solid or a liquid but, it will only reach these states if put under extreme temperature or pressure. Helium is the second most abundant element, right after hydrogen. Helium comes from radioactive decay and is one of the lightest elements on Earth.[1]. We use it for balloons because it is so light and also because it is not flammable so the balloons do not burst into flames.

Occurrences

In 1895 Sir William Ramsey discovered that helium could be obtained from a mineral containing uranium, which is called clevite. Today most helium is collected from natural gas deposits. Most of these deposits are located in Kansas, Oklahoma and Texas.[2] The first evidence of helium was discovered in space in 1868. Pierre Janssen noticed a yellow spectrographic line surrounding the sun during a solar eclipse he witnessed. This yellow line was caused by Helium. Norman Lockyer discovered the yellow line that same year, he and an English chemist named Edward Frankland named the element Helios(the Greek word for sun). In 1903 the US discovered gas in Kansas and when it was analyzed, they discovered that 1.84% of the gas that they sampled was Helium.[3]

Uses

Helium balloons

Helium is used in balloons and blimps because it is lighter than air so it will float, although hydrogen is lighter -- and easier to obtain -- it is highly flammable so helium is used instead for safety. Helium is also used in scuba tanks that divers wear. It is combined with oxygen so that deep sea divers can breath air that has no nitrogen in it. Otherwise they could get Nitrogen Narcosis when they change depth quickly, because the sudden change in pressure allows Nitrogen to form very painful bubbles in their blood. [4]

Helium is also useful because it can be made very cold without freezing solid. Liquid Helium is used to cool down some metals to reach superconductivity. Since it tends to not become radioactive, it is used as a coolant gas in some Nuclear reactors. [5]

Isotopes

Helium atom (not to scale)

Main Article: Isotopes

Isotopes are atoms of the same element that have different numbers of neutrons. We are aware of eight isotopes for the element helium. Out of those eight only two are stable; helium-3 and helium-4. In the atmosphere there are thousands of helium-4 atoms for each helium-3 atom. Helium-4 is produced by alpha decay from radioactive elements. Helium-3 is very abundant in stars because it is a product of nuclear fusion. Helium-5, 6, 7, and 8 all have very short half-lives, lasting only a few seconds each.[6] Helium-5, helium-6, and helium-8 have been combined with the stable isotopes of helium to form stable helium compounds. Helium-4 is the most unique isotope of helium since it can form into two different types of liquid. Those two liquids are liquid helium-1 and liquid helium-2. Liquid helium-1 has properties like normal liquids while liquid helium-2 is very different(for example, it can flow uphill) it is formed when liquid helium-1 is cooled to a temperature below 2.18K. [7]

History of Helium

Helium was first discovered by Pierre Janssen, a French astronomer, in 1868. He noticed it during a solar eclipse in Guntur India when the light of the corona, the atmosphere surrounding the sun, showed evidence of a new element. A few decades later on March 26, 1895 a British chemist by the name of William Ramsey found out how to produce Helium from a mineral called cleveite by treating it with mineral acids. He was looking for Argon which is also a Noble Gas but instead found Helium. Scientists continued to study the gas and in 1895 the chemists Abraham Langlet and Per Teodor Cleve, both from Sweden, found that the average atomic weight of helium was 4.003. In 1908, a Dutch physicist named Heike Kamerlingh Onnes discovered how to liquefy helium. He cooled the gas to less than one degree Kelvin but even at this temperature was unable to turn it into a solid. One of his students, Willem Hendrik Keesom, was able to solidify helium in 1926. He did that by applying 25 atmospheres of pressure to the gas.[8]

A representation of a Helium atom.

Evidence for a Young Earth

Main Article: Helium diffusion

One type of nuclear decay is the emission of Helium nuclei known as an alpha emission. Elements like uranium and thorium produce helium in zircons as a by-product of their radioactivity. This helium migrates out of zircons quickly over a wide range of temperatures. If the zircons really are about 1.5 billion years old (the age which conventional dating gives assuming a constant decay rate), almost all of the helium should have dissipated from the zircons long ago. But there is a significant amount of helium still inside the zircons, showing their ages to be 6000 +/- 2000 years. Accelerated decay may have produced a billion years worth of helium in that short amount of time.