Several applications exist that capitalize on properties of the various isotopes of a given element. Isotope separation is a significant technological challenge, particularly with heavy elements such as uranium or plutonium. Lighter elements such as lithium, carbon, nitrogen, and oxygen are commonly separated by gas diffusion of their compounds such as CO and NO. The separation of hydrogen and deuterium is unusual since it is based on chemical rather than physical properties, for example in the Girdler sulfide process. Uranium isotopes have been separated in bulk by gas diffusion, gas centrifugation, laser ionization separation, and (in the Manhattan Project) by a type of production mass spectroscopy.
Use of chemical and biological properties
• Isotope analysis is the determination of isotopic signature, the relative abundances of isotopes of a given element in a particular sample. For biogenic substances in particular, significant variations of isotopes of C, N and O can occur. Analysis of such variations has a wide range of applications, such as the detection of adulteration of food products.[8]The identification of certain meteorites as having originated on Mars is based in part upon the isotopic signature of trace gases contained in them.[9]
• Another common application is isotopic labeling, the use of unusual isotopes as tracers or markers in chemical reactions. Normally, atoms of a given element are indistinguishable from each other. However, by using isotopes of different masses, they can be distinguished by mass spectrometry or infrared spectroscopy. For example, in 'stable isotope labeling with amino acids in cell culture (SILAC)' stable isotopes are used to quantify proteins. If radioactive isotopes are used, they can be detected by the radiation they emit (this is calledradioisotopic
labeling).
• A technique similar to radioisotopic labeling is radiometric dating: using the known half-life of an unstable element, one can calculate the amount of time that has elapsed since a known level of isotope existed. The most widely known example is radiocarbon dating used to determine the age of carbonaceous materials.
• Isotopic substitution can be used to determine the mechanism of a reaction via the kinetic isotope effect.
Use of nuclear properties
• Several forms of spectroscopy rely on the unique nuclear properties of specific isotopes. For example, nuclear magnetic resonance (NMR) spectroscopy can be used only for isotopes with a nonzero nuclear spin. The most common isotopes used with NMR spectroscopy are 1H,2D,15N, 13C, and31P.
• Mössbauer spectroscopy also relies on the nuclear transitions of specific isotopes, such as57Fe.
• Radionuclides also have important uses. Nuclear power and nuclear weapons development require relatively large quantities of specific isotopes.
See also
• Atom
• Table of nuclides
• Radionuclide (or radioisotope)
• Nuclear medicine (includes medical isotopes)
• Isotopomer
• List of particles
• Isotopes are nuclides having the same number of protons; compare:
• Isotones are nuclides having the same number of neutrons.
• Isobars are nuclides having the same mass number, i.e. sum of protons plus neutrons.
• Nuclear isomers are different excited states of the same type of nucleus. A transition from one isomer to another is accompanied by emission or absorption of a gamma ray, or the process of internal conversion. (Not to be confused with chemical isomers.)
• Bainbridge mass spectrometer
External links
• Nucleonica Nuclear Science Portal[10]
• Nucleonica Nuclear Science Wiki[11]
• International Atomic Energy Agency[12]
• Atomic weights of all isotopes[13]
• Atomgewichte, Zerfallsenergien und Halbwertszeiten aller Isotope[14]
• Chart of the Nuclides[15]produced by the Knolls Atomic Power Laboratory $25
• Exploring the Table of the Isotopes[16]at the LBNL
• Current isotope research and information[17]
• Radioactive Isotopes[18]by the CDC
• Interacive Chart of the nuclides, isotopes and Periodic Table[19]
• The LIVEChart of Nuclides - IAEA[20]with isotope data, in Java[20]or HTML[21]
References
[1] IUPAC http://goldbook.iupac.org/I03331.html
[2] "Radioactives Missing From The Earth" (http://www.don-lindsay-archive.org/creation/isotope_list.html). . [3] "NuDat 2 Description" (http://www.nndc.bnl.gov/nudat2/help/index. jsp). .
[4] Budzikiewicz H, Grigsby RD (2006). "Mass spectrometry and isotopes: a century of research and discussion". Mass spectrometry reviews 25 (1): 146 – 57. doi:10.1002/mas.20061. PMID 16134128.
[5] Sonzogni, Alejandro. "Interactive Chart of Nuclides" (http://www.nndc.bnl.gov/chart/). National Nuclear Data Center: Brook haven National Laboratory. .
[6] hhttp://bryza.if.uj.edu.pl/zdfk/wp-includes/publications/misiaszek_180mTa_2009.pdf Search for the radioactivity of 180mTa using an underground HPGe sandwich spectrometer, 2009
[7] (http://www.don-lindsay-archive.org/creation/isotope_list.html)
[8] E. Jaminet al.(2003). "Improved Detection of Added Water in Orange Juice by Simultaneous Determination of the Oxygen-18/Oxygen-16 Isotope Ratios of Water and Ethanol Derived from Sugars"" (http://pubs.acs.org/cgi-bin/article.cgi/jafcau/2003/51/i18/pdf/jf030167&
nbsp;m.pdf). J. Agric. Food Chem.51: 5202. doi:10.1021/jf030167 m. .
[9] A. H. Treiman, J. D. Gleason and D. D. Bogard (2000). ""The SNC meteorites are from Mars"" (http://www.sciencedirect.com/
science?_ob=ArticleURL&_udi=B6V6T-41WBDHD-8&_user=2400262&_coverDate=10/31/2000&_alid=678948366&_rdoc=3&
_fmt=summary&_orig=search&_cdi=5823&_sort=r&_docanchor=&view=c&_ct=89&_acct=C000057185&_version=1&
_urlVersion=0&_userid=2400262&md5=c5ae2aa8ea60dbd76c2870048730a299). Planet. Space. Sci.48: 1213.
doi:10.1016/S0032-0633(00)00105-7. . [10] http://www.nucleonica.net
[11] http://www.nucleonica.net/wiki/index.php/Special:Allpages/Help:
[12] http://www.IAEA.org
[13] http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&ascii=html&isotype=some [14] http://atom.kaeri.re.kr/
[15] http://www.chartofthenuclides.com/
[16] http://ie.lbl.gov/education/isotopes.htm [17] http://www.isotope.info/
[18] http://www.bt.cdc.gov/radiation/isotopes/
[19] http://www.yoix.org/elements.html [20] http://www-nds.iaea.org/livechart
[21] http://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
Orbital
Anatomic orbitalis a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom.[1]This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus. These functions may serve as three-dimensional graph of an electron’s likely location. The term may thus refer directly to the physical region defined by the function where the electron is likely to be.[2]Specifically, atomic orbitals are the possible quantum states of an individual electron in the collection of electrons around a single atom, as described by the orbital function.
Despite the obvious analogy to planets revolving around the Sun, electrons cannot be described as solid particles and so atomic orbitals rarely, if ever, resemble a planet's elliptical path. A more accurate analogy might be that of a large and often oddly-shaped atmosphere (the electron), distributed around a relatively tiny planet (the atomic nucleus).
Atomic orbitals exactly describe the shape of this atmosphere only when a single electron is present in an atom.
When more electrons are added to a single atom, the additional electrons tend to more evenly fill in a volume of space around the nucleus so that the resulting collection (sometimes termed the atom’s “electron cloud” [3]) tends toward a generally spherical zone of probability describing where the atom’s electrons will be found.
Electron atomic and molecular orbitals. The chart of orbitals (left) is arranged by increasing energy (see Madelung rule). Note that atomic orbits are functions of three variables (two angles, and the distance from the nucleus, r). These images are faithful to
the angular component of the orbital, but not entirely representative of the orbital as a whole.
The idea that electrons might revolve around a compact nucleus with definite angular momentum was convincingly argued in 1913 by Niels Bohr,[4] and the Japanese physicist Hantaro Nagaoka published an orbit-based hypothesis for electronic behavior as early as 1904.[5] However, it was not until 1926 that the solution of the Schrödinger equation for electron-waves in atoms provided the functions for the modern orbitals.[6]
Because of the difference from classical mechanical orbits, the term
"orbit" for electrons in atoms, has been replaced with the term orbital —a term first coined by chemist Robert Mulliken in 1932.[7] Atomic orbitals
are typically described as“hydrogen-like”(meaning one-electron) wave functions over space, categorized byn,l, and m quantum numbers, which correspond to the electrons' energy, angular momentum, and an angular momentum direction, respectively. Each orbital is defined by a different set of quantum numbers and contains a maximum of
two electrons. The simple names s
Computed hydrogen atom orbital for n=6, l=0, m=0 orbital, p orbital, d orbital and f
orbital refer to orbitals with angular momentum quantum numberl= 0, 1, 2 and 3 respectively. These names indicate the orbital shape and are used to describe the electron configurations as shown on the right. They are derived from the characteristics of their spectroscopic lines: sharp, principal, diffuse, and f undamental, the rest being named in alphabetical order (omitting j).[8] [9]
From about 1920, even before the advent of modern quantum mechanics, the aufbau principle (construction principle) that atoms were built up of pairs of electrons, arranged in simple repeating patterns of increasing odd numbers (1,3,5,7..), had been used by Niels Bohr and others to infer the presence of something like atomic
orbitals within the total electron configuration of complex atoms. In the mathematics of atomic physics, it is also often convenient to reduce the electron functions of complex systems into combinations of the simpler atomic orbitals. Although each electron in a multi-electron atom is not confined to one of the “one-or-two-electron atomic orbitals” in the idealized picture above, still the electron wave-function may be broken down into combinations which still bear the imprint of atomic orbitals; as though, in some sense, the electron cloud of a many-electron atom is still partly “composed” of atomic orbitals, each containing only one or two electrons. The physicality of this view is best illustrated in the repetitive nature of the chemical and physical behavior of elements which results in the natural ordering known from the 19th century as the periodic table of the elements. In this ordering, the repeating periodicity of 2, 6, 10, and 14 elements in the periodic table corresponds with the total number of electrons which occupy a complete set of s,p,dandf atomic orbitals, respectively.