Home Science Chemistry Top Questions Show What is an isotope?Why do isotopes have different properties?When are isotopes stable?How were isotopes discovered?Summary Read a brief summary of this topicisotope, one of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behaviour but with different atomic masses and physical properties. Every chemical element has one or more isotopes. An atom is first identified and labeled according to the number of protons in its nucleus. This atomic number is ordinarily given the symbol Z. The great importance of the atomic number derives from the observation that all atoms with the same atomic number have nearly, if not precisely, identical chemical properties. A large collection of atoms with the same atomic number constitutes a sample of an element. 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. Not all the atoms of an element need have the same number of neutrons in their nuclei. In fact, it is precisely the variation in the number of neutrons in the nuclei of atoms that gives rise to isotopes. Hydrogen is a case in point. It has the atomic number 1. Three nuclei with one proton are known that contain 0, 1, and 2 neutrons, respectively. 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. Many important properties of an isotope depend on its mass. The total number of neutrons and protons (symbol A), or mass number, of the nucleus gives approximately the mass measured on the so-called atomic-mass-unit (amu) scale. The numerical difference between the actual measured mass of an isotope and A is called either the mass excess or the mass defect (symbol Δ; see table). Abundances of the isotopes
The specification of Z, A, and the chemical symbol (a one- or two-letter abbreviation of the element’s name, say Sy) in the form AZSy identifies an isotope adequately for most purposes. Thus, in the standard notation, 11H refers to the simplest isotope of hydrogen and 23592U to an isotope of uranium widely used for nuclear power generation and nuclear weapons fabrication. (Authors who do not wish to use symbols sometimes write out the element name and mass number—hydrogen-1 and uranium-235 in the examples above.) The term nuclide is used to describe particular isotopes, notably in cases where the nuclear rather than the chemical properties of an atom are to be emphasized. The lexicon of isotopes includes three other frequently used terms: isotones for isotopes of different elements with the same number of neutrons, isobars for isotopes of different elements with the same mass number, and isomers for isotopes identical in all respects except for the total energy content of the nuclei. Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now What represents A pair of isotopes?Thus, isotopes have same atomic number (Z), but different mass number (A). That means, the elements having different atomic numbers (protons) are not isotopes. 612L and 614L are isotopes of same element with 6 and 8 neutrons respectively.
Which two elements form A pair of isotopes?Hydrogen and Deuterium are isotopes with same atomic number but different mass number. Hydrogen have atomic number 1 and mass number 1 where as deuterium have atomic number 1 but mass number 2. Was this answer helpful?
What are 2 examples of isotopes?These isotopes are radioactive in nature and are, therefore, known as radioisotopes (or radionuclides). Examples of radioactive isotopes include carbon-14, tritium (hydrogen-3), chlorine-36, uranium-235, and uranium-238.
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