Atomic radius/Å: 0.49
covalent radius/Å: 0.93
Electronic configuration: 1s2
Oxidation state: 0
Norman Lockyer and Edward Frankland in 1868 during an eclipse of the sun, from observations of the solar spectrum.
In the universe, helium is second only to the hydrogen is the second most abundant elements.
Used for deep-sea diving, fermenter research, nuclear energy system cooling agent.
State: light odourless, colorless, odorless inert gases. Melting point (℃) : 272.05
Boiling point (℃) : 268.785
Density (g/L / 273 K, 26 ATM) : 0.1785
Than hot/J/gK: 5.193
Melting hot/KJ/mol: 5.23
Coefficient of thermal conductivity/W/cmK: 0.00152
Abundance retention time/year:
The sun (relative to the H = 1 x 1012) : 6.31 x 1010 sea/P.P.M. : 4 x 10-6
The earth's crust/P.P.M. : 0.008
Atmospheric/P.P.M. (volume) : 5.2
The human body the content in liver/P.P.M. : zero
Organs: muscle/P.P.M. : zero
Blood/mg dm-3: trace th intake:
Bone/P.P.M. : zero (70 Kg) are total body:
Helium, atomic number 2, atomic weight 4.002602 for the rare gas a. Element name comes from the Greek, original intention is "the sun". 1868 was used to observe the sun spectroscope would surface, found a new yellow chromatographic line, and that is the sun, belongs to the unknown elements on the name helium. Someone with inorganic acid treatment after asphalt by a uranium not lively gas, in 1895 the British scientists ramsay with spectrum proof is helium. In succession again after from other mineral, air and gas to found the helium. Helium content in the earth's crust is few, in the entire universe in accordance with the quality plan in 23%, second only to hydrogen. Helium in the air content is 0.0005%. There are two kinds of helium natural isotope: helium 3, helium 4, the nature of existence is basically complete helium helium 4.
Helium is normally for a colorless, odorless gas; Melting point-272.2 ° C (25 atmospheres), boiling point-268.9 ° C; Density 0.1785 g/l, 267.8 ° C critical temperature, atmospheric pressure critical pressure 2.26; The water solubility 8.61 cm ³ / kg water. Helium is not only in the standard atmospheric pressure cured of the material. Liquid helium in the temperature dropped to 2.18 K, nature mutations, become a super fluid, can move upward along the vessel wall, thermal conductivity for copper 800 times, and become a superconductor; The specific heat capacity, surface tension, compressibility is abnormal.
Helium is the least active element, basically do not form any compounds. The application of helium is mainly as a protection gas, gas-cooled reactor work of fluid and ultra-low temperature coolant and so on.