Isotopes Definition and Examples in Chemistry

Isotopes Definition and Examples in Chemistry Isotopes [ahy-suh-tohps]  are atoms with the same number of protons, but differing numbers of neutrons. In other words, the have different atomic weights. Isotopes are different forms of a single element. Key Takeaways: Isotopes Isotopes are samples of an element with different numbers of neutrons in their atoms.The number of protons for different isotopes of an element does not change.Not all isotopes are radioactive. Stable isotopes either never decay or else decay very slowly. Radioactive isotopes undergo decay.When an isotope decays, the starting material is the parent isotope. The resulting material is the daughter isotope. There are 275 isotopes of the 81 stable elements. There are over 800 radioactive isotopes, some of which are natural and some synthetic. Every element on the periodic table has multiple isotope forms. The chemical properties of isotopes of a single element tend to be nearly identical. The exception would be the isotopes of hydrogen  since the number of neutrons has such a significant effect on the size of the hydrogen nucleus. The physical properties of isotopes are different from each other since these properties often depend on mass. This difference may be used to separate isotopes of an element from each other by using fractional distillation and diffusion. With the exception of hydrogen, the most abundant isotopes of the natural elements have the same number of protons and neutrons. The most abundant form of hydrogen is protium, which has one proton and no neutrons. Isotope Notation There are a couple of common ways to indicate isotopes: List the mass number of an element after its name or element symbol. For example, an isotope with 6 protons and 6 neutrons is carbon-12 or C-12. An isotope with 6 protons and 7 neutrons is carbon-13 or C-16. Note the mass number of two isotopes may be the same, even though they are different elements. For example, you could have carbon-14 and nitrogen-14.The mass number may be given in the upper left side of an element symbol. (Technically the mass number and atomic number should be stacked in line with each other, but they dont always line up on a computer.) For example, the isotopes of hydrogen may be written:11H,  21H,  31H Isotope Examples Carbon 12 and Carbon 14 are both isotopes of carbon, one with 6 neutrons and one with 8 neutrons (both with 6 protons). Carbon-12 is a stable isotope, while carbon-14 is a radioactive isotope (radioisotope). Uranium-235 and uranium-238 occur naturally in the Earths crust. Both have long half-lives. Uranium-234 forms as a decay product. Related Words Isotope (noun), Isotopic (adjective), Isotopically (adverb), Isotopy (noun) Isotope Word Origin and History The term isotope was introduced by the British chemist Frederick Soddy in 1913, as recommended by Margaret Todd. The word means having the same place from the Greek words isos equal (iso-) topos place. Isotopes occupy the same place on the periodic table even though isotopes of an element have different atomic weights. Parent and Daughter Isotopes When radioisotopes undergo radioactive decay, the initial isotope may be different from the resulting isotope. The initial isotope is called the parent isotope, while the atoms produced by the reaction are called daughter isotopes. More than one type of daughter isotope may result. As an example, when  U-238 decays into Th-234, the uranium atom is the parent isotopes, while the thorium atom is the daughter isotope. A Note About Stable Radioactive Isotopes Most stable isotopes dont undergo radioactive decay, but a few do. If an isotope undergoes radioactive decay very, very slowly, it may be termed stable. An example is bismuth-209. Bismuth-209 is a stable radioactive isotope that undergoes alpha-decay, but has a half-life of 1.9 x 1019 years (which is more than a billion times longer than the estimated age of the universe). Tellurium-128 undergoes beta-decay with a half-life estimated to be 7.7 x 1024 years! Historical References Alexander Thomas Cameron,  Radiochemistry  (London, England: J. M. Dent Sons, 1910), p. 141. Soddy, Frederick. Intra-atomic charge. Nature 92, Springer Nature Publishing AG, 1913.. Strà ¶mholm, Daniel and Svedberg, Theodor (1909) Untersuchungen à ¼ber die Chemie der radioactiven Grundstoffe II. (Investigations into the chemistry of the radioactive elements, part 2),  Zeitschrift fà ¼r anorganischen Chemie,  63: 197–206. Thomson, J. J. (1912). XIX. Further experiments on positive rays.  Philosophical Magazine. Series 6.  24  (140): 209.

Philosophical Quotes on Violence

Philosophical Quotes on Violence What is violence? And, accordingly, how should non-violence be understood? While I have written a number of articles on these and related topics, it is useful to look at how philosophers have synthesized their views on violence. Here is a selection of quotes, sorted out into topics. Voices on Violence Frantz Fanon: Violence is man re-creating himself.George Orwell: We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm.Thomas Hobbes: In the first place, I put for a general inclination of all mankind a perpetual and restless desire of power after power, that ceaseth only in death. And the cause of this is not always that a man hopes for a more intensive delight than he has already attained to, or that he cannot be content with a moderate power, but because he cannot assure the power and means to live well, which he hath present, without the acquisition of more.Niccolà ² Machiavelli: Upon this, one has to remark that men ought either to be well treated or crushed, because they can avenge themselves of lighter injuries, of more serious ones they cannot; therefore the injury that is to be done to a man ought to be of such a kind that one does not stand in fear of revenge.Niccolà ² Machiavelli: I say that every prince must desire to be considered merciful and not cruel. He must, however, take care not to misuse this mercifulness. [†¦] A prince, therefore, must not mind incurring the charge of cruelty for the purpose of keeping his subjects united and confident; for, with a very few examples, he will be more merciful than those who, from excess of tenderness, allow disorders to arise, from whence spring murders and rapine; for these as a rule injure the whole community, while the executions carried out by the prince injure only one individual [†¦] From this arises the question whether it is better to be loved more than feared, or feared more than loved. The reply is, that one ought to be both feared and loved, but as it is difficult for the two to go together, it is much safer to be feared than loved, if one of the two has to be wanting. Against Violence Martin Luther Kind Jr.: The ultimate weakness of violence is that it is a descending spiral, begetting the very thing it seeks to destroy. Instead of diminishing evil, it multiplies it. Through violence you may murder the liar, but you cannot murder the lie, nor establish the truth. Through violence you may murder the hater, but you do not murder hate. In fact, violence merely increases hate. So it goes. Returning violence for violence multiplies violence, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness: only light can do that. Hate cannot drive out hate: only love can do that.Albert Einstein: Heroism by order, senseless violence, and all the pestilent nonsense that goes by the name of patriotism- how I hate them! War seems to me a mean, contemptible thing: I would rather be hacked in pieces than take part in such an abominable business.Fenner Brockway: I had long put on one side the purist pacifist view that one should have nothing to do with a social revolution if any violence were involved... Nevertheless, the conviction remained in my mind that any revolution would fail to establish freedom and fraternity in proportion to its use of violence, that the use of violence inevitably brought in its train domination, repression, cruelty. Isaac Asimov: Violence is the last refuge of the incompetent.