Argon abundance

In conventional K- Ar dating, the abundance of potassium is measured on one aliquot of the sample and the argon abundance and isotopic composition are measured on another. The... 

Murer, Ch. A., Baur, H., Signer, P., Wider, R. (1997) Helium, neon, and argon abundances in the solar wind In vacuo etching of meteoritic iron-nickel. Geochim. Cosmochim. Acta, 61, 1303-14. 

Fisher DE (1978) Terrestrial potassium and argon abundances as limits to models of atmospheric evolution. In Alexander EC, Ozima M (ed) Terrestrial Rare Gases. Center for Academic Publications Japan, Tokyo, p 173-183... 

The possibility that an even larger impact caused the P T extinction received support when Becker and Poreda found that helium and argon atoms were present in the inner cores of some of the fullerenes from the P T boundary sediments (The cover of this book shows a helium atom inside a mol ecule of Ceo) What is special about the fullerene trapped atoms is that the mixtures of both helium and argon isotopes resemble extraterrestrial isotopic mixtures more than earthly ones The He/ He ratio in the P T boundary fullerenes for example is 50 times larger than the natural abundance ratio... 

For several reasons — including the complete breakdown of sample into its substituent elements in the plasma and the use of an unreactive monatomic plasma gas (argon) — background interferences in the resulting mass spectra are of little importance. Since there are no or very few background overlaps with sample ions, very precise measurements of sample ion abundances can be made, which facilitate the determination of precise isotope ratios. 

Gases and volatile materials can be swept into the center of an argon plasma flame, where they are fragmented into ions of their constituent elements. The m/z values of ions give important information for identification of the elemental composition of a sample, and precise measurement of ion abundances is used to provide accurate isotope ratios. 

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 major constituents of unpolluted air (not including water) at ground level are iritrogerr (78.08%) and oxygen (20.95%). The next most abundant constituents are argon (at 0.934%) and carbon dioxide (about 0.0.34%), followed by the other noble gases ... 

Except for argon, the third-row elements make up an important fraction (about 30%) of the earth s crust. Silicon and aluminum are the second and third most abundant elements (oxygen is the most abundant). Both the occurrence and the mode of preparation of each element can be understood in terms of trends in chemistry discussed earlier in this chapter. 

Isotopes are also used to determine properties of the environment. Just as carbon-14 is used to date organic materials, geologists can determine the age of very old substances such as rocks by measuring the abundance in rocks of radioisotopes with longer half-lives. Uranium-238 (t1/2 = 4.5 Ga, 1 Ga = 10y years) and potassium-40 (t,/2 = 1.26 Ga) are used to date very old rocks. For example, potassium-40 decays by electron capture to form argon-40. The rock is placed under vacuum and crushed, and a mass spectrometer is used to measure the amount of argon gas that escapes. This technique was used to determine the age of rocks collected on the surface of the Moon they were found to be 3.5-4.0 billion years old, about the same age as the Earth. 

The Zag meteorite fell in the western Sahara of Morocco in August 1998. This meteorite was unusual in that it contained small crystals of halite (table salt), which experts believe formed by the evaporation of brine (salt water). It is one of the few indications that liquid water, which is essential for the development of life, may have existed in the early solar system. The halite crystals in the meteorite had a remarkably high abundance of 128Xe, a decay product of a short-lived iodine isotope that has long been absent from the solar system. Scientists believe that the iodine existed when the halite crystals formed. The xenon formed when this iodine decayed. For this reason, the Zag meteorite is believed to be one of the oldest artifacts in the solar system. In this lab, you will use potassium-argon radiochemical dating to estimate the age of the Zag meteorite and the solar system. 

Bogard D. D. and Garrison D. H. (1998). Relative abundances of argon, krypton, and xenon in the Martian atmosphere as measured in Martian meteorites. Geochimica et Cosmochimica Acta, 62(10) 1829-1835. 

The reactions of small cluster cations of copper and silver, Cu and Ag (n = 1-5), with methanol, ethanol, the two isomers of propanol, and the four isomers of butanol have been studied in a FT-ICR mass spectrometer (200). The ions were produced by FAB and exited through a small hole that aided the clustering process. Once in the cell, the ions were collisionally cooled with argon and allowed to react with the alcohols (3-100 x 10 6 Pa) for periods up to 60 s. The Cu4 ion was produced but was of insufficient abundance for reactivity studies. 

Oxides are a common issue since they can make up to several percent of the metal beam, while compounds of argon and atmospheric gasses, such as ArN, are ubiquitous. The abundance... 

ISOTOPES There are a total of 24 isotopes of argon, three of which are stable. They are Ar-36, which constitutes just 0.3365% of the natural amount of argon Ar-38, which contributes just 0.0632% to the amount of argon on Earth and Ar-40, which, by far, constitutes the most argon on Earth, 99.6003% of its natural abundance. 

Argon is a colorless, odorless, tasteless, chemically inert noble gas that makes up about 0.93% of the Earths atmosphere. It is the third most abundant gas in the atmosphere, meaning it is more common than carbon dioxide, helium, methane, and hydrogen. 

Argon is the 56th most abundant element on Earth. It is the most abundant of all the noble gases found in the atmosphere. In fact, the only source of argon is the atmosphere, where it is found at just under 1% of air by volume. 

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