Helium

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Image

Attribution: Alchemist-hp

Animated Helium

History

From the Greek word helios, the sun. Janssen obtained the first evidence of helium during the solar eclipse of 1868 when he detected a new line in the solar spectrum. Lockyer and Frankland suggested the name helium for the new element. In 1895 Ramsay discovered helium in the uranium mineral cleveite while it was independently discovered in cleveite by the Swedish chemists Cleve and Langlet at about the same time. Rutherford and Royds in 1907 demonstrated that alpha particles are helium nuclei.

Sources

Except for hydrogen, helium is the most abundant element found in the universe. Helium is extracted from natural gas. In fact, all natural gas contains at least trace quantities of helium.

It has been detected spectroscopically in great abundance, especially in the hotter stars, and it is an important component in both the proton-proton reaction and the carbon cycle, which account for the energy of the sun and stars.

The helium content of the atmosphere is about 1 part in 200,000. While it is present in various radioactive minerals as a decay product, the bulk of the Free World's supply is obtained from wells in Texas, Oklahoma, and Kansas. Outside the United States, the only known helium extraction plants, in 1984 were in Eastern Europe (Poland), the USSR, and a few in India.

Isotopes

Seven isotopes of helium are known: Liquid helium (He-4) exists in two forms: He-4I and He-4II, with a sharp transition point at 2.174K. He-4I (above this temperature) is a normal liquid, but He-4II (below it) is unlike any other known substance. It expands on cooling, its conductivity for heat is enormous, and neither its heat conduction nor viscosity obeys normal rules.

General Info

AtomicNumber
2
Symbol
He
Name
Helium

Atomic Info

Appearance
AtomicWeight
4.002602(2)
Color
D9FFFF
ElectronicConfiguration
1s2
ElectronegativityInPauling
AtomicRadiusInPM
32
IonRadiusInPM
VanDerWaalsRadiusInPM
140
IEinKJmol
2372
EAinKJmol
0
OxidationStates
StandardState
gas
BondingType
atomic
MeltingPoint
0.95
BoilingPoint
4
Density
0
State
Noble gas
DiscoveredYear
1868