A recommendation letter or letter of recommendation, also known as a letter of reference, reference letter or simply reference, is a document in which the writer assesses the qualities, characteristics, and capabilities of the person being recommended in terms of that individual's ability to perform a particular task or function.
This article is about stable isotope ratios. For the general category of stable nuclides, see Stable nuclide. The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element.his article is about stable isotope ratios. For the general category of stable nuclides, see Stable nuclide. The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element.
radioactive isotope, also called radioisotope, any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy â¦ by spontaneously emitting radiation in the form of alpha, beta, and gamma rays. Every chemical element has one or more radioactive isotopes.For example, hydrogen, the lightest element, has three isotopes with mass numbers 1, 2, and 3. Only hydrogen-3 (tritium), however, is a radioactive isotope, the other two being stable. More than 1,000 radioactive isotopes of the various elements are known. radioactive isotope is a form of an element that is unstable and eventually decays into a different element. For example, most Carbon has 6 protons and 6 neutrons, and is st â¦ able.