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Stable isotopes of neon are produced in stars. Neon's most abundant isotope 20 Ne (90.48%) is created by the nuclear fusion of carbon and carbon in the carbon-burning process of stellar nucleosynthesis. This requires temperatures above 500 megakelvins, which occur in the cores of stars of more than 8 solar masses. [31] [32]
The abundances of the naturally occurring isotopes of neon. Neon (10 Ne) possesses three stable isotopes: 20 Ne, 21 Ne, and 22 Ne. In addition, 17 radioactive isotopes have been discovered, ranging from 15 Ne to 34 Ne, all short-lived. The longest-lived is 24 Ne with a half-life of 3.38(2) min. All others are under a minute, most under a second.
Neon has three main stable isotopes: 20 Ne, 21 Ne and 22 Ne, with 20 Ne produced by cosmic nucleogenic reactions, causing high abundance in the atmosphere. [ 97 ] [ 103 ] 21 Ne and 22 Ne are produced in the earth's crust as a result of interactions between alpha and neutron particles with light elements; 18 O, 19 F and 24,25 Mg. [ 104 ]
Of the 26 "monoisotopic" elements that have only a single stable isotope, all but one have an odd atomic number—the single exception being beryllium. In addition, no odd-numbered element has more than two stable isotopes, while every even-numbered element with stable isotopes, except for helium, beryllium, and carbon, has at least three.
Neon has a high first ionization potential of 21.564 eV, which is only exceeded by that of helium (24.587 eV), requiring too much energy to make stable ionic compounds. Neon's polarisability of 0.395 Å 3 is the second lowest of any element (only helium's is more extreme).
Neon also forms an unstable hydrate. [23] There is some empirical and theoretical evidence for a few metastable helium compounds which may exist at very low temperatures or extreme pressures. The stable cation [HeH] + was reported in 1925, [24] but was not considered a
The noble gases (helium, neon, argon, krypton, xenon and radon) were previously known as 'inert gases' because of their perceived lack of participation in any chemical reactions. The reason for this is that their outermost electron shells (valence shells) are completely filled, so that they have little tendency to gain or lose electrons.
The noble gases (helium, neon, argon, krypton, xenon, and radon) are also gases at STP, but they are monatomic. The homonuclear diatomic gases and noble gases together are called "elemental gases" or "molecular gases", to distinguish them from other gases that are chemical compounds. [2]