Helium universal abundance

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

As the universe expanded it cooled and the positively charged protons and helium nuclei com bined with electrons to give hydrogen and helium atoms Together hydrogen and helium account for 99% of the mass of the universe and 99 9% of its atoms Hydrogen is the most abundant element 88 6% of the atoms in the universe are hydrogen and 11 3% are helium... 

Helium is the second most abundant element in the universe (76% H, 23% He) as a result of its synthesis from hydrogen (p. 9) but, being too light to be retained by the earth s gravitational field, all primordial helium has been lost and terrestrial helium, like argon, is the result of radioactive decay ( He from a-decay of heavier elements, " °Ar from electron capture by... 

The majority of the Universe is made from hydrogen and helium produced during the Big Bang, although some He has been made subsequently. The relative cosmic abundance of some of the elements relevant to the formation of life is given in Table 1.2, with all elements heavier than H, He and Li made as a result of fusion processes within stars, as we shall see later. The cosmic abundance is assumed to be the same as the composition of the Sun. 

Helium is the second most abundant element in the visible Universe and accordingly there is a mass of data from optical and radio emission lines in nebulae, optical emission lines from the solar chromosphere and prominences and absorption lines in spectra of hot stars. Further estimates are derived more indirectly by applying theories of stellar structure, evolution and pulsation. However, because of the relative insensitivity of Tp to cosmological parameters, combined with the need to allow for additional helium from stellar nucleosynthesis in most objects, the requirements for accuracy are very severe better than 5 per cent to place cosmological limits on Nv and better still to place interesting constraints on t] or One can, however, assert with confidence that there is a universal floor to the helium abundance in observed objects corresponding to 0.23 < Fp < 0.25. 

The overall abundance of helium and heavy elements in the Universe today. This reflects the total effect of fuel consumption and nucleosynthesis by all the stars that ever existed. Roughly speaking, one may consider this in two... 

We know a great deal about the nature of the universe. For instance, the element hydrogen makes up about 75% of all the mass in the universe. In terms of number, about 90% of all atoms in the universe are hydrogen atoms, and most of the rest of the atoms in the universe are helium. All the other heavier elements make up just one to two percent of the total. Interestingly, the most abundant element on Earth (in number of atoms) is oxygen (O ). Oxygen accounts for about 50% of all the elements found in the Earth s crust, and silicon, the second most abundant element, makes up about 25%. Silicon dioxide (SiO ) accounts for about 87% of the total Earth s mass. Sfiicon dioxide is the main chemical compound found in sand and rocks. 

Carbon is the I4th most abundant element, making up about 0.048% of the Earths crust. It is the sixth most abundant element in the universe, which contains 3.5 atoms of carbon for every atom of silicon. Carbon is a product of the cosmic nuclear process called fusion, through which helium nuclei are burned and fused together to form carbon atoms with the atomic number 12. Only five elements are more abundant in the universe than carbon hydrogen, helium, oxygen, neon, and nitrogen. 

Helium is the 73rd most abundant element on Earth, but it is the second most abundant element in the universe, after hydrogen. Together, helium and hydrogen make up 99.9% of all the elements in the universe, but hehum makes up only a small trace of the elements on Earth. 

They carry the stamp of the Big Bang, whence their great interest for cosmology. Their lithium content in particular is a precious clue as to the nucleonic density of the Universe, combined with deuterium and helium abundances measured in extremely metal-poor media (see Appendix 1). 

Why are elemental hydrogen and helium, the two most abundant elements in the universe, not present in significant amounts in the Earth s atmosphere ... 

Helium, the second most abundant element in the universe after hydrogen, is rare on Earth because its atoms are so light that a large proportion of them reach high speeds and escape from the atmosphere. However, it is found as a component of natural gases trapped under rock formations (notably in Texas), where it has collected as a result of the emission of a particles by radioactive elements. An a particle is a helium nucleus (4He2+), and an atom of the element forms when the particle picks up two electrons from its surroundings. 

The chemical composition of the Universe is primarily estimated from models of the Big Bang (Delsemme, 1998, 19-42) and spectrographic analyses of nebulas and the atmospheres of stars (Krauskopf and Bird, 1995, 563-564). Currently, hydrogen and helium are the most abundant elements, representing 71% and 28%, respectively, of all known matter in the Universe (Delsemme, 1998, 22). Arsenic has been ranked as the 39th most common element in the Universe with an average concentration of 0.008 mg kg-1 (Matschullat, 2000, 299 Table 3.1). 

Helium is a very special element, second only to hydrogen in cosmologic importance. It is by a large margin the second most abundant elementin the universe. This is thought to be the result of a Big Bang beginning to the universe. 

The firstlarge supply ofterrestrial helium on Earth was discovered in 1903 when drillers opened a huge pocket of natural gas near Dexter, Kansas. A quarter million cubic meters of gas spewed forth daily. Residents were amazed when it extinguished a flaming bale of hay rather than producing a huge torch. TWo University of Kansas chemistry professors identified it to contain abundant helium. 

---