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Dalam [[nomenklatur]] ilmiah, isotop (nuklida) dispesifikasikan berdasarkan nama unsur tertentu oleh sebuah "hyphen" dan jumlah nukleon (proton dan neutron) dalam nukleus atom (misal, helium-3, [[carbon-12]], [[carbon-14]], iron-57, [[uranium-238]]). Dalam bentuk simbolik, jumlah nukleon ditandakan sebagai sebuah prefik naik-ke-atas terhadap [[simbol kimia]] (misal, <sup>3</sup>He, <sup>12</sup>C, <sup>14</sup>C, <sup>57</sup>Fe, <sup>238</sup>U).
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*[[Tabel isotop ( lengkapterpisah)]] .▼== Variation in properties between isotopes ==
*[[Tabel isotop (lengkap)]].
In a neutral atom, the number of [[electron]]s equals the number of protons. Thus, different isotopes of a given element also have the same number of electrons and the same electronic structure. Because the chemical behavior of an atom is largely determined by its electronic structure, isotopes exhibit nearly identical chemical behavior. The primary exception is that, due to their larger masses, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element. (This phenomenon is termed the [[kinetic isotope effect]]).
*[[Tabel isotop|Tabel beberapa isotop dari unsur-unsur ringan]].
This "mass effect" is most pronounced for [[protium]] (<sup>1</sup>H) vis-à-vis [[deuterium]] (<sup>2</sup>H), because deuterium has twice the mass of protium. For heavier elements the relative mass difference between isotopes is much less, and the mass effect is usually negligible.
Similarly, two [[molecules]] which differ only in the isotopic nature of their atoms (''[[isotopologue]]s'') will have nearly identical electronic structure, and therefore have similar physical and chemical properties. The [[molecular vibration|vibrational mode]]s of a molecule are determined by its shape and by the masses of its constituent atoms. Consequently, isotopologues will have different sets of vibrational modes. Since vibrational modes allow a molecule to absorb [[photon]]s of corresponding energies, isotopologues have different optical properties in the [[infrared]] range.
Although isotopes exhibit nearly identical electronic and chemical behavior, their nuclear behavior varies dramatically. Atomic nuclei consist of protons and neutrons bound together by the [[strong nuclear force]]. Because protons are positively charged, they repel each other. Neutrons, which are electrically neutral, allow some separation between the positively charged protons, reducing the electrostatic repulsion and stabilizing the nucleus. For this reason neutrons are necessary for two or more protons to be bound into a nucleus. As the number of protons increases, additional neutrons are needed to form a stable nucleus; for example, although the neutron/proton ratio of <sup>3</sup>He is 1/2, the neutron/proton ratio of <sup>238</sup>U is greater than 3/2. If too many neutrons or too few neutrons are present, the nucleus becomes unstable and subject to [[nuclear decay]].
== Occurrence in nature ==
Several isotopes of each element can be found in nature. The [[relative abundance]] of an isotope is strongly correlated with its tendency toward [[nuclear decay]]; short-lived nuclides quickly decay away, while their long-lived counterparts endure. However, this does not mean that short-lived species disappear entirely; many are continually produced through the decay of longer-lived nuclides. The tabulated [[atomic mass]]es of elements are averages that account for the presence of multiple isotopes with different masses.
According to generally accepted [[cosmology]], virtually all nuclides other than isotopes of [[hydrogen]] and [[helium]] were built in [[star]]s and [[supernova]]e. Their respective abundances here result from the quantities formed by these processes, their spread through the [[galaxy]], and their rates of decay. After the initial coalescence of the [[solar system]], isotopes were redistributed according to mass (see also [[Solar system#Origin and evolution of the Solar System|Origin of the solar system]]). The isotopic composition of elements is different on different planets, making it possible to determine the origin of [[meteorite]]s.
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== Applications of isotopes ==
Several applications exist that capitalize on properties of the various isotopes of a given element.
=== Use of chemical properties ===
* One of the most common applications 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]] (see "Properties"). If radioactive isotopes are used, they can be detected by the radiation they emit (this is [[radioisotopic labelling]]).
* A technique similar to radioisotopic labelling is [[radiometric dating]] (most famously [[radiocarbon dating]]). It can be used to study chemical processes that the experimenter does not witness, by using naturally-occurring isotopic tracers.
* 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 <sup>1</sup>H, <sup>2</sup>D, <sup>13</sup>C, and <sup>31</sup>P.
* [[Mossbauer spectroscopy|Mössbauer spectroscopy]] also relies on the nuclear transitions of specific isotopes, such as <sup>57</sup>Fe.
* [[Radionuclide]]s also have important uses. [[Nuclear power]] and [[nuclear weapon]]s development require relatively large quantities of specific isotopes. The process of [[isotope separation]] represents a significant technological challenge.
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*[[Tabel isotop (terpisah)]] - table of all known isotopes
▲*[[Tabel isotop (lengkap)]]
*[[Tabel nuklida]]
*[[Daftar partikel]]
* Isotopes are nuclides having the same number of protons; compare:
** [[Isotone]]s are nuclides having the same number of neutrons.
** [[Isobar]]s are nuclides having the same mass number, i.e. sum of protons plus neutrons.
** [[Nuclear_isomer|Nuclear isomer]]s 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 [[isomer]]s.)
== Pranala luar ==
*[http://ie.lbl.gov/education/isotopes.htm Exploring the Table of the Isotopes] at the [[LBNL]]
[[ CategoryKategori:Isotop| * ]] ▼<!--Categories-->
[[ CategoryKategori: FisikaKimia nuklir]] ▼[[CategoryKategori:KimiaFisika nuklir]]
▲[[Category:Fisika nuklir]]
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[[af:Isotoop]]
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