Isotopos (en ingles)

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  • Publicado : 30 de mayo de 2011
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Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes. In other words, Isotopes are different types ofatoms of the same chemical element, each having a different number of neutrons. In a corresponding manner, isotopes differ in mass number, or number of nucleons but never in atomic number. The number ofprotons, the atomic number, is the same because that is what characterizes a chemical element. A nuclide is an atomic nucleus with a specified composition of protons and neutrons. The nuclide conceptemphasizes nuclear properties over chemical properties, while the isotope concept emphasizes chemical over nuclear. An isotope and/or nuclide is specified by the name of the particular element (thisindicates the atomic number implicitly) followed by a hyphen and the mass number When a chemical symbol is used standard notation is to indicate the number of nucleons with a superscript at the upperleft of the chemical symbol and to indicate the atomic number with a subscript at the lower left.

Chemical and molecular properties

A neutral atom has the same number of electrons as protons.Thus, different isotopes of a given element all have the same number of protons and electrons and share a similar electronic structure. Because the chemical behavior of an atom is largely determined byits electronic structure, different isotopes exhibit nearly identical chemical behavior. The main exception to this is the kinetic isotope effect: due to their larger masses, heavier isotopes tend toreact somewhat more slowly than lighter isotopes of the same element.

Nuclear properties and stability

Atomic nuclei consist of protons and neutrons bound together by the residual strong force.Because protons are positively charged, they repel each other. Neutrons, which are electrically neutral, stabilize the nucleus in two ways. Their copresence pushes protons slightly apart, reducing the...
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