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Helium is the least water-soluble monatomic gas, [96] and one of the least water-soluble of any gas (CF 4, SF 6, and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10 −5, respectively, versus helium's 0.70797 x 2 /10 −5), [97] and helium's index of refraction is closer to unity than that of any other gas. [98]
The reason is that there is no primordial helium in the atmosphere; due to the small mass of the atom, helium cannot be retained by the Earth's gravitational field. [71] Helium on Earth comes from the alpha decay of heavy elements such as uranium and thorium found in the Earth's crust, and tends to accumulate in natural gas deposits. [71]
In Earth's atmosphere, the ratio of 3 He to 4 He is 1.343(13) × 10 −6. [5] However, the isotopic abundance of helium varies greatly depending on its origin. In the Local Interstellar Cloud , the proportion of 3 He to 4 He is 1.62(29) × 10 −4 , [ 6 ] which is ~121 times higher than in Earth's atmosphere.
That’s where helium comes in: With a boiling point of minus 452 degrees Fahrenheit, liquid helium is the coldest element on Earth. Pumped inside an MRI magnet, helium lets the current travel ...
Helium is inert - it does not react with other substances or combust - and its atomic number is 2, making it the second lightest element after hydrogen. Rockets need to achieve specific speeds and ...
The volume fraction of the main gases in Earth's atmosphere according to height. The heterosphere is above about 100 km in the graph. The heterosphere of Earth begins at about 100 km altitude and extends to the outer reaches of its atmosphere. [3] It incorporates most of the thermosphere and all of the exosphere. The major constituents of Earth ...
Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. [1] Helium's first ionization energy of 24.57 eV is the highest of any element. [2]
While helium-4 is common on Earth, helium-3 is more readily found elsewhere in the cosmos, which is why scientists were surprised to detect a larger amount of the element than had been previously ...