What is an isotope?

Answer 1

An isotope is any of several different forms of an element each having different mass. Isotopes of an element will have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers, which give the total number of nucleons—the number of protons plus neutrons. The word isotope, from Greek meaning at the same place, comes from the fact that all isotopes of an element are located at the same place on the periodic table.

A nuclide is any particular atomic nucleus with a specific atomic number Z and mass number A; it is equivalently an atomic nucleus with a specific number of protons and neutrons. Collectively, all the isotopes of all the elements form the set of nuclides. The distinction between the terms isotope and nuclide has somewhat blurred, and they are often used interchangeably. Isotope is best used when referring to several different nuclides of the same element; nuclide is more generic and is used when referencing only one nucleus or several nuclei of different elements. For example, it is more correct to say that an element such as fluorine consists of one stable nuclide rather than that it has one stable isotope.

In scientific nomenclature, isotopes and nuclides are specified by the name of the particular element, implicitly giving the atomic number, followed by a hyphen and the mass number (e.g. helium-3, carbon-12, carbon-14, iodine-131 and uranium-238). In symbolic form, the number of nucleons is denoted as a superscripted prefix to the chemical symbol (e.g. 3He, 12C, 14C, 131I and 238U).

Contents
1 Variation in properties between isotopes
2 Occurrence in nature
3 Molecular mass of isotopes
4 Applications of isotopes
4.1 Use of chemical properties
4.2 Use of nuclear properties
5 See also
6 External links




Variation in properties between isotopes
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 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 main exception to this is the kinetic isotope effect: due to their larger masses, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element.

This "mass effect" is most pronounced for protium (1H) vis-à-vis deuterium (2H), 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 (isotopologues) will have identical electronic structure and therefore almost indistinguishable physical and chemical properties (again with deuterium providing the primary exception to this rule). The vibrational modes 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 photons 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. Neutrons also stabilize the nucleus because at short ranges they attract each other and protons equally by the strong nuclear force, and this also offsets the electrical repulsion between protons. For this reason, one or more 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 to proton ratio of 3He is 1:2, the neutron/proton ratio of 238U is greater than 3:2. If too many or too few neutrons are present, the nucleus is unstable and subject to nuclear decay.


Occurrence in nature
Most elements have several different isotopes that 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. Also, short-lived isotopes such as those of promethium have been detected in the spectra of stars, where they presumably being continuously made by stellar nucleosynthesis. The tabulated atomic masses 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 (and traces of some isotopes of lithium, beryllium and boron-- see big bang nucleosynthesis) were built in stars and supernovae. 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 Origin of the solar system). The isotopic composition of elements is different on different planets, making it possible to determine the origin of meteorites.

Molecular mass of isotopes
The molecular mass (Mr) of an element is determined by its nucleons. For example, Carbon-12 has 6 Protons and 6 Neutrons. When a sample contains two or more isotopes the equation below is applied:



Where Mr(1) and Mr(2) are the molecular masses of each individual isotope, and %abundance is the percentage abundance of that isotope in the sample.

Applications of isotopes
Several applications exist that capitalize on properties of the various isotopes of a given elements

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 labeling).
A technique similar to radioisotopic labelling 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, and 31P.
Mössbauer spectroscopy also relies on the nuclear transitions of specific isotopes, such as 57Fe.
Radionuclides also have important uses. Nuclear power and nuclear weapons development require relatively large quantities of specific isotopes. The process of isotope separation represents a significant technological challenge

Answer 2

An isotope can be defined as atoms of same element having same atomic number but a different mass number.Suppose there's an element X with atomic number (no. of protons)=3 and mass number 4(protons +neutrons).Then it means that the no.of neutrons = 4-3=1.But if there is another atom ,of the same element X,with 2 electrons then its mass no. = 3+2 =5.(mind you the no. of protons does not change!).This atom of X shall be reffered to as an isotope.
Most elements have isotopes.And it is due to these isotopes that the atomic mass of elements are not whole numbers(thus creating a problem for students who find it hard to remember the atomic masses of different elements).

Answer 3

An isotope is any of several different forms of an element each having different mass. Isotopes of an element will have nuclei with the same number of protons (the same atomic number) but different numbers of neutrons. Therefore, isotopes have different mass numbers, which give the total number of nucleons—the number of protons plus neutrons. The word isotope, from Greek meaning at the same place, comes from the fact that all isotopes of an element are located at the same place on the periodic table.

A nuclide is any particular atomic nucleus with a specific atomic number Z and mass number A; it is equivalently an atomic nucleus with a specific number of protons and neutrons. Collectively, all the isotopes of all the elements form the set of nuclides. The distinction between the terms isotope and nuclide has somewhat blurred, and they are often used interchangeably. Isotope is best used when referring to several different nuclides of the same element; nuclide is more generic and is used when referencing only one nucleus or several nuclei of different elements. For example, it is more correct to say that an element such as fluorine consists of one stable nuclide rather than that it has one stable isotope.

In scientific nomenclature, isotopes and nuclides are specified by the name of the particular element, implicitly giving the atomic number, followed by a hyphen and the mass number (e.g. helium-3, carbon-12, carbon-14, iodine-131 and uranium-238). In symbolic form, the number of nucleons is denoted as a superscripted prefix to the chemical symbol (e.g. 3He, 12C, 14C, 131I and 238U).

Detailsa at
http://en.wikipedia.org/wiki/Isotope

Answer 4

isotope
One of two or more species of atoms of a chemical element having nuclei with the same number of protons but different numbers of neutrons. They have the same atomic number and hence nearly identical chemical behaviour but different atomic masses. Most elements found in nature are mixtures of several isotopes; tin, for example, has 10 isotopes. In most cases, only stable isotopes of elements are found in nature. The radioactive forms break down spontaneously into different elements (see radioactivity). Isotopes of all elements heavier than bismuth are radioactive; some occur naturally because they have long half-lives.

Answer 5

Elemental substances are composed of atoms.
Atoms consist of protons, electrons and neutrons.
Protons weigh 1 and neutrons weigh 1 and electrons weigh 0.
Among these atoms are different isotopes.
Isotopes have different atomic weights but the same atomic number.
Atomic numbers reflect the number of protons in the nucleus of the atom, while the atomic weight reflects the sum of the number of protons and the number of neutrons.
So essentially the difference between isotopes of a given element is a differing number of neutrons.

Some notable isotopes
Oxygen 16, 18
Carbon 12, 14
Hydrogen 1, 2, 3(deuterium,tritium)

Answer 6

Isotopes of an element are the different species of that element that exist in the nature.The atoms of these elements have different number of neutrons but same number of protons in their nucleus.Example- Hydrogen element(1 proton,no neutron) has 2 isotopes-Deuterium(1 proton,1 neutron) and Tritium(1 proton,2 neutrons)

Answer 7

A sportsteam for Springfield. Go Springfield Isotopes!

Answer 8

hi
isotope of an atom is that which has same atomic no. but different Mass no. or it can also be defined as the electrons are same in no. but neutrons differ in no. i think this would help u

Answer 9

isotope --
a chemical element with same atomic number but different atomic weight

Example:
Hydrogen
Deuterium
Tritium

Answer 10

Forms of a chemical element that have the same number of protons (atomic number) but different numbers of neutrons and different atomic weights

Answer 11

Diamond is an isotope of carbon because its has the same no. of protons but diff. no of electrons..