Isotopes | Stable & Unstable | Applications | Definitions | Diagnosis | Radiotherapy | Biochemical Analysis Diagnostic/Therapeutic Radiopharmaceuticals | Discovery | Isotopes in Medicine | Terms & Concepts An isotope is one of two or more species of atoms of a chemical element with the same atomic number (same number or protons in the nucleus) and position in the periodic table and nearly identical chemical behavior but with different atomic masses and physical properties. An atom is first identified and labeled according to the number of protons in its nucleus.
A bar of pure uranium, for instance, would consist entirely of atoms with atomic number 92.The periodic table of the elements assigns one place to every atomic number, and each of these places is labeled with the common name of the element, as, for example, calcium, radon, or uranium.The energies involved are so large, and the nucleus is so small that physical conditions in the Earth (i.e. The rate of decay or rate of change of the number N of particles is proportional to the number present at any time, i.e.The half-life is the amount of time it takes for one half of the initial amount of the parent, radioactive isotope, to decay to the daughter isotope.To see how we actually use this information to date rocks, consider the following: Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.
By definition, D* = N-1) (2) Now we can calculate the age if we know the number of daughter atoms produced by decay, D* and the number of parent atoms now present, N.Not all the atoms of an element need have the same number of neutrons in their nuclei. Three nuclei with one proton are known that contain 0, 1, and 2 neutrons, respectively.In fact, it is precisely the variation in the number of neutrons in the nuclei of atoms that gives rise to isotopes. The three share the place in the periodic table assigned to atomic number 1 and hence are called isotopes (from the Greek isos, meaning "same," and topos, signifying "place") of hydrogen.The only problem is that we only know the number of daughter atoms now present, and some of those may have been present prior to the start of our clock. The reason for this is that Rb has become distributed unequally through the Earth over time.We can see how do deal with this if we take a particular case. For example the amount of Rb in mantle rocks is generally low, i.e. The mantle thus has a low If these two independent dates are the same, we say they are concordant., in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. Soddy in explaining aspects of radioactivity the first stable isotope (of neon) was discovered by J. Thus isotopes of a given element have identical chemical properties but slightly different physical properties and very different half-lives, if they are radioactive (see half-life ).