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Bismuth No Longer the Heaviest Stable Element

forii writes "Bismuth-209 was commonly thought to be the heaviest stable element. But now Physicists have discovered that Bi-209 actually is unstable and decays with a halflife of 2*10^19 years. This means that the average 8oz (237ml) bottle of Pepto-Bismol contains one decay event every 36 hours or so."

78 comments

  1. be sure dont use this element in any project that has a life span of > 2*10^19 years!

    --
    I am the bastard of base minus 12! Turing was the ejaculate of my complete machine!
    1. Re:So... by Anonymous Coward · · Score: 0

      if a bismuth shat in the woods...would anybody care?

  2. I can see the headlines now... by renehollan · · Score: 4, Funny
    Pepto-Bismol DANGER!!!

    [shock-rag wire service] Scientists discover that bismuth, a major component of Pepto-Bismol , is RADIOACTIVE and decays into the TOXIC POISON thallium.

    While the decay rate is the slowest observed to date and, in fact, sets a record, it is noted that NO MINIMUM SAFE EXPOSURE LEVEL has been established for radiation exposure, and there is NO CURE for thallium posioning.

    --
    You could've hired me.
    1. Re:I can see the headlines now... by Deanasc · · Score: 1

      Yeah and the article will end with a pitch to sell some Colloidal Silver machines. After all Colloidal Silver is natures antibiotic.

      --
      I've hit Karma 50 and gotten a Score:5, Troll... I win!
  3. Actually... by Mensa+Babe · · Score: 2, Interesting

    Bismuth-209 was commonly thought to be the heaviest stable element.

    Actually, most of the scientists believed it was stable, however not everyone. (Some of them were considered "crackpots" by the rest of the community, but the point remains valid, even if somewhat less so.) Try a Google search.

    --
    Karma: Positive (probably because of superiour intellect)
  4. And the new winner is? by cookd · · Score: 1

    The obvious question that immediately came to my mind was "what is the new 'commonly-accepted heaviest stable element'"? And that question doesn't seem to be answered by the posting or the article. Anybody know the answer? Thanks.

    --
    Time flies like an arrow. Fruit flies like a banana.
    1. Re:And the new winner is? by Anonymous Coward · · Score: 1

      Lead. Pb(208)

    2. Re:And the new winner is? by ConceptJunkie · · Score: 2, Informative

      If you look at the periodic table, the answer is obviously the next smaller element, lead, which is what most of the heavier elements eventually decay to.

      --
      You are in a maze of twisty little passages, all alike.
    3. Re:And the new winner is? by The+Briguy · · Score: 1

      It might not nessisarly be lead, (although I'm pretty sure your right), since there could have been some lighter isotope of bismuth which was stable (208, 207, etc).

    4. Re:And the new winner is? by gooberguy · · Score: 1

      True, but then it would be lighter than lead. D/\ Gooberguy

      --


      Karma: Meh (Mostly from meh.)
    5. Re:And the new winner is? by The+Briguy · · Score: 1

      actually, if it were bismuth 208, it would still be heavier then lead (208), since a proton wieghs more then a neutron. By the way, this is all academic, since Bismuth 208 is the only (realitively) stable isotope anyway

    6. Re:And the new winner is? by Anonymous Coward · · Score: 0

      I think you have it backwards. A neutron weighs more than a proton, since a neutron weighs as much as a proton plus an electron plus whatever the binding energy is.

    7. Re:And the new winner is? by barawn · · Score: 1

      Not true - this is what's told to people a lot of times in basic science classes, but it's wrong. A neutron is not a bound state of a proton and an electron. It's a bound state of two d quarks and a u quark. Inverse beta decay (electron capture) happens when an electron emits a virtual W-, turning into an electron neutrino, and the virtual W- interacts with the u quark in the proton, turning it into a d quark.

      So the proper answer is, a neutron weighs more than a proton, because a neutron is mass of proton plus the mass difference between a u and d quark, and the binding energy difference between the uud and the udd combination. The mass of an electron doesn't enter into it at all (at least, in the standard model. It might in other theories).

      The main reason this is true is because a neutron isn't a bound state - it isn't stable. It decays when absolutely nothing overcomes its binding energy into a proton, an electron, and an electron antineutrino.

    8. Re:And the new winner is? by Anonymous Coward · · Score: 0

      Yes, but not enough to make a difference. You must also realize that a Bi-208 or Pb-208 atom is not just a collection of unbound neutron and protons as well. The more tightly they are bound, the lighter the atom becomes. So, it is possible for either to be the heavyweight depending on how far they sit down in their potential. In this case, Bi-208 weighs 207.979717 and Pb-208 weighs 207.976627 (u). If they were just protons and neutron and electrons added together, they would be 209.7326 and 209.7334 respectively. -tm

    9. Re:And the new winner is? by barawn · · Score: 1

      Um. Yes. I never disputed that. However, you're making it sound random as to which is heavier. In fact, it's NOT possible for Pb-208 to be the heavier of the two, considering the fact that Bi-208 has one more proton than Pb-208. The (residual) nuclear strong force has isospin symmetry due to the approximate chiral symmetry, which means that the strong binding force is equivalent between 208 protons, 208 neutrons, and any internal combination thereof.

      The electric repulsive force, however, is clearly greater with Bi-208 than Pb-208, because Bi-208 has an extra charge +1 in its nucleus, therefore, it must be less bound.

      In other words:

      Pb-208: V_Pb = F_em(82 protons) - F_s(208 hadrons)
      Bi-208: V_Bi = F_em(82 protons)*(83^2)/(82^2) - F_s(208 hadrons)

      Obviously V_Bi = V_Pb + F_em(82 protons)*(83^2/82^2 - 1)

      and since the second term is strictly greater than zero, the binding is less for V_Bi (more bound = more negative, less bound = less negative = more positive).

      Obviously Tl-208 is going to weigh less, and Po-208 is going to weigh more.

    10. Re:And the new winner is? by The+Briguy · · Score: 1

      oops. Brain freeze. Your right, of course. Neutrons wiegh slightly more then protons. But, like I said, its all academic anyway.

  5. Thanks for posting this after markets are closed by Anonymous Coward · · Score: 1, Funny

    All that portfolio I had of Bismute stocks, bonds and futures are going to be worthless by Monday morning. Knew should've bought oxygen - stable although slow-growth stock, my broker told me people are always gonna need oxygen, but no, I wanted the red-hot high-yield stock.

  6. Hence the term "commonly" by rk · · Score: 1

    The subject says it all.

  7. And yet... by Deanasc · · Score: 1

    Nobody ever worries about Francium poisoning.

    --
    I've hit Karma 50 and gotten a Score:5, Troll... I win!
  8. 2*10^19? by Niahak · · Score: 3, Interesting

    That's a really long time. I mean, really long. The universe is considered to be 15 to 20 billion years by most who decide to actually guess. That means that, if the universe is 20 billion years old... and 1 g of Bi-209 was produced at the beginning of the universe, it would take another 1.999999998*10^19 years before half of the Bi-209 was left. I wonder if our universe will even reach that age, if the big bang 'cycle' theory holds to be true.

  9. Re:Thanks for posting this after markets are close by Lord+Sauron · · Score: 1

    Actually your stocks are going to be worth half of its original value in 2*10^19 years, not monday morning.

    What proves that, even it's not considered stable anymore, it's still much more stable than Amazonium (from the IPv4 group in the Periodic Table) or Enronium.

  10. It's dangerous? KILL IT!!! by slittle · · Score: 2, Funny

    OMG, you're right! At one event per 36 hours, it's practically a fucking Omega Particle!

    Someone call Starfleet! *KILL IT! *KILL IT!

    (*read: start a new government agency dedicated to the analysis and monitoring of this tool-of-terrorists; fund a few dozen fact-finding junkets, c/o the taxpayer; draft an array of pointless laws regarding Bi research, don't forget to call the religious end-of-world nutters for their valuable insight; end up hiring a PR agency to divert attention away from the fact that you've accomplished bugger all, were wrong all along, and now have a $30mil mansion on the harbour).

    --
    Opportunity knocks. Karma hunts you down.
  11. For the non-chemists/physisicists like me... by Andy_R · · Score: 2, Interesting

    Does 'stable' mean that decay hasn't been observed, or that it NEVER occurs?

    How does quantum mechanics apply to decay?

    Does an atom decay when a certain set of positions occur within it, and if so why can't the frequency that this would occur at be calculated?

    --
    A pizza of radius z and thickness a has a volume of pi z z a
    1. Re:For the non-chemists/physisicists like me... by metamathica · · Score: 5, Informative
      Disclaimer: my degree in physics qualifies me to paint a general picture here. Technical nitpicks are always welcome.


      In the article, it mentions that people actually have predicted this decay using theory. The nucleus is not completely understood, but the theory of basic decay phenomena is pretty complete.

      Any time you talk about the quanta of physics, you need to use quantum mechanics. The quanta are of course the so-called fundamental particles, including the proton, neutron and electron.

      The nucleus is held together by the strong force. This force must be very strong to keep the protons, whose like charge repels one another, very close together. The strong force only pulls over very short distances: if some nucleons get far enough, their electromagnetic repulsion will continue to push each other apart and they will be separated permanently.

      However, the particles in the nucleus don't have enough energy to get over the hump, so nuclei are stable. This is where quantum mechanics applies. Even if the hump is very tall, the nonlocality of quantum mechanics means that some particles can escape if the hump isn't very wide. Because they have a probabilistic spread in space, some of them can creep to the other side. When they get lucky like this, a nuclear decay occurs. The details of the nucleus determine how high the barrier and how wide the hump, both of which affect the probability of tunneling.

      In stable nuclei, particles are prohibited from escaping. In this case, it's not that the hump is too high, but that it's asymmetrical. If the nuclear force is strong enough compared to the energy of the nucleons, it can dig a deep well for the particles. In this case, having some possibility of getting past the hump doesn't really help: the area on the other side of the hump is prohibited regardless.

      One way to think of this process is to say that quantum mechanics would allow you to borrow the energy you need to jump over a fence as long as you fell back down on the other side, no matter how tall the fence.

      But you can't keep the borrowed energy, so you could never jump to the top of a roof, even if it were no taller than the wall you just jumped over.

    2. Re:For the non-chemists/physisicists like me... by Squiffy · · Score: 1

      "Disclaimer: my degree in physics qualifies me to paint a general picture here. Technical nitpicks are always welcome."

      I don't have a physics degree, but I'm pretty sure I understand that the Weak force can alter quark flavor, and that this constitutes a completely different decay mechanism from the one you described (not that the one you described is wrong). Am I confused?

    3. Re:For the non-chemists/physisicists like me... by metamathica · · Score: 2, Informative
      I was completely amazed that someone modded me troll until I saw your comment! ;-) I have no complaints about honest dialog though. It may be too late for many others to read this, but at least you seem interested.

      You are right about the role of the weak force. The process you are thinking of is beta decay. In this process a neutron is converted into a proton, an electron and an antineutrino.

      Beta decay is detected by looking for beta particles, also known as electrons. This is another interesting process, but the article mentions that they looked for and found alpha particles.

      I hope this makes things clearer. Incidentally, we've talked about two of the three kinds of radiation here:

      • Alpha Radiation consists of alpha particles, which are helium nuclei (no electrons). These particles are not particularly stable since they are heavy and have high charge. They travel no more than an inch or so in air and are stopped by skin. Alpha sources are not dangerous unless eaten or inhaled. In fact some smoke detectors measure the rate of emission from radioactive americium because alpha particles are stopped by smoke.
      • Beta Radiation consists of beta particles, which are electrons. Beta radiation penetrates your body easily and is quite dangerous. The primary danger is the possibility of genetic damage from beta particles tearing through your body.
      • Gamma Radiation consists of gamma particles, which are photons. These are the particles of light. X-rays, microwaves, ultraviolet, visible, infrared, radio and TV waves, etc. are all systems of photons of varying energies. Gamma radiation is highly dangerous, comparable to beta radiation; X-rays are dangerous in high doses but much safer than gamma rays. Lower frequencies like those of cell phones and microwaves may pose some health risk though studies have at least shown it is not dramatic. Photons are emitted by moving charged particles with energy to spare. Thus, gamma radiation often accompanies other nuclear radiation as an aftereffect of another decay mechanism.
    4. Re:For the non-chemists/physisicists like me... by Squiffy · · Score: 1

      Even idiots get to be moderators, I guess. Thanks for the info. =*)

    5. Re:For the non-chemists/physisicists like me... by gumbi+west · · Score: 1

      But you can't keep the borrowed energy, so you could never jump to the top of a roof, even if it were no taller than the wall you just jumped over.

      Well, most of the time you can't keep the energy. Hawking Radiation is, however, a case where one of the particles does get to keep the borrowed energy.

      Hawking Radiation is covered will in this USA today article.

    6. Re:For the non-chemists/physisicists like me... by barawn · · Score: 1

      Not really. He's talking about energy that's 'borrowed' from the vacuum. A different way of saying it is that the energy that a particle possesses isn't really an 'exact' quantity, but a distribution, and a small fraction of the time it's going to be actually have enough energy to leap the gap. Gaussians distributions are nice that way...

      Hawking radiation is where you're borrowing energy from the black hole, not the vaccuum. That's why you can 'keep' it - because it's actually just a very slow reaction of a black hole with the vaccuum.

  12. First Nitpick Post! by fm6 · · Score: 4, Informative
    Bismuth-209 is not an element. Bismuth is the element -- Bismuth-209 is one of its isotopes. So the headline should read, "Bismuth no longer the heaviest element with a stable isotope". Except that's misleading too -- it sounds like they've found one even heavier. How about... oh, never mind.

    Incidentally, all elements have unstable isotopes. Bismuth's are pretty rare, but they do exist!

    Bismuth obsessive will rejoice in the web site of the Bismuth Producers Association.

    I prefer Tums, myself.

  13. Second Nitpick Post! by slug359 · · Score: 4, Informative

    Bismuth-209 is the most common isotope of bismuth (with its mean atomic mass being 208.98038), so it would be acceptable to say ' Bismuth No Longer the Heaviest Stable Element', according to webelements and The Jefferson Lab.

  14. Third Nitpick Post by fm6 · · Score: 1

    Technically correct, but still misleading. It suggests there's a new stable element heavier than Bismuth. (Yeah, chemistry/math geeks know the stable part of the periodic table is full. But most people don't. Certainly not the writers at Stargate SG-1.) How about, "Bismuth not stable; Polonium now heaviest stable element."

    1. Re:Third Nitpick Post by bobowla · · Score: 3, Informative

      How about "Bismuth not stable; Lead now heaviest stable element". (Polonium has no stable isotopes).

    2. Re:Third Nitpick Post by fm6 · · Score: 2, Funny

      Ok, not only did you catch me in a dyslexism, you came up with a better headline. For that you will suffer!

  15. So at the big crunch... by fm6 · · Score: 2, Funny

    ...Pepto Bismal will be in short supply. And just when people really need it!

  16. Check those numbers by Anonymous Coward · · Score: 0

    My last Pepto experiment after the 7-layer burrito incident showed a dramatically higher level of decay events as well as some highly unstable isotopes of sulfur.

  17. Francium? Freedomium by infernalC · · Score: 4, Funny

    GAITHERSBURG, MD
    22 May 2003

    Today, the National Institute for Standards and Technology, the civilian agency of the US Government responsible for researching and making available data concerning the physical properties of substances including chemical elements, annouces the discontinued use of francium as the name of the 87th chemical element.

    "It's just not appropriate to continue to refer to an element by the name of a nation whose inaction is tantamount to condoning terrorism," said Dr. Hratch G. Semerjian, director of the Chemical Science and Technology Laboratory. "We decided that it would be better to refer to the 87th element as Freedomium in honor of those who died to secure the liberty of our country.

    Asked if the agency would once again return to calling the 87th element francium, Semerjian said that the element would not return to its former name. "We are prepared to take whatever action is necessary to liberate any element whose nomenclature is derived from a repressive regime."

    -

    1. Re:Francium? Freedomium by k98sven · · Score: 1

      Today, the National Institute for Standards and Technology, the civilian agency of the US Government responsible for researching and making available data concerning the physical properties of substances including chemical elements, annouces the discontinued use of francium as the name of the 87th chemical element.

      Actually, the International Union of Pure and Applied Chemistry is the governing body on element names..

  18. Re:It's dangerous? KILL IT!!! by clem.dickey · · Score: 2, Funny

    > At one event per 36 hours

    Remember, that's just an average. Your experience may be different. It could decay all at once just after you swallow. You can't be too careful.

  19. "Contained" is right! by Markus+Registrada · · Score: 3, Interesting
    Imagine my surprise at finding that Slashdot got something right: forii wrote that a "bottle of Pepto-Bismol contains one decay event" every 36 hours, and it does! Those alpha particles can't get through the glass.

    Not only that, he never said "it's" when he meant "its".

    My favorite element, by the way, is Osmium. It sublimates dreadfully toxic fumes from a solid state at room temperature, and nobody knows exactly what its specific gravity is, nor whether it or Iridium is the heaviest element.

    1. Re:"Contained" is right! by PateraSilk · · Score: 1

      here's a nice link.

      --
      Danke tres mucho, tovarishch.
    2. Re:"Contained" is right! by Idarubicin · · Score: 1
      Imagine my surprise at finding that Slashdot got something right: forii wrote that a "bottle of Pepto-Bismol contains one decay event" every 36 hours, and it does! Those alpha particles can't get through the glass...

      ...whether it or Iridium is the heaviest element.

      Look, if you're going to sarcastic, I'm afraid that I have to nitpick your post. The question is whether osmium or iridium is the densest element, not the heavest.

      Quite right that the alphas can't get through the glass--they won't even travel an appreciable distance through the liquid Pepto in the bottle.

      --
      ~Idarubicin
  20. Heaviest Stable Element? by Anonymous Coward · · Score: 0

    I can see it now...

    Let the Cowboy Neal jokes fly!

  21. Proton decay by reverseengineer · · Score: 4, Interesting
    "Other kinds of decays such as protons from proton-rich nuclei could be studied by the same method but this will have to be proved!"

    This could prove to be the most important use of this technique, as most proposed Grand Unified Theories have interactions that can turn quarks into leptons, so that a proton would be expected to eventually decay into a positron and a meson. Unfortunately, this process has never been observed (well, only somewhat unfortunately, as high proton stability is definitely a Good Thing in most ways), and experiment and theory have thus set a lower bound on the lifetime of a proton of roughly 10^33 years, about 23 orders of magnitude greater than the estimated current age of the universe.

    As you can see, compared to the suggested lifetime of a proton, even Bi-209 seems unstable. The expected extreme rarity of a proton decay event, however, is somewhat balanced by the overwhelming abundance of protons in the universe.The "lifetime" for an individual proton is more like a life expectancy, an average figure- given a suitably large collection of protons, odds are good that at least one would decay in a reasonable timeframe. If you carefully watch 10^33 protons for a year, for example, and reality agrees with theory (big if), then it is likely (certainly not guaranteed though) you will see at least one decay event. Now, 10^33 may sound like a tremendous amount, but remember that each proton has a mass of only 1.67*10^-27 kilograms, so that 10^33 protons would have a mass of about 1,600 metric tons- a lot, but not outrageous.

    The real problem lies in that "carefully watching" part. So many other forms of radiation are much more prevalent, and so might mask the signature of proton decay. Cosmic rays, naturally occuring radioisotopes in places you'd never think to look, solar neutrinos, that sort of thing. Ah, why yes, this is one of those experiments they do in a salt mine and uses a gigantic tank of ultrapure water (your proton source). However, as of yet, no one has found concrete evidence for proton decay from one of these experiments. Go here for a excellent site about a proton decay detector that ran in the 80s, and here for one currently in use.

    Perhaps this process will detect this very rare event, lending profound support to one of the many supersymmetric models out there. Unfortunately, if it does not detect proton decay, it will be much more difficult to say just what the result means, it being difficult to prove a negative and all.

    --
    "FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
  22. Orange Alert! by Anonymous Coward · · Score: 0

    Al Queda may even now be building a dirty bomb out of a trailer full fertilizer, diesel and Pepto Bismol.

  23. somewhat OT isotope question by frovingslosh · · Score: 3, Interesting

    Since there are likely to be a number of people teading this that have good command of the topic, let me ask a question on isotopes. All through school I was taught that different isotopes of an element have the same chemical property. That information is still found in most articles on the subject. Yet I recently found a reference that Heavy Water was poisonous. Since there is no radiation danger, how can heavy water be poisonous if isotopes are chemically identical? What is going on here? And what are the indications of heavy water poisoning?

    --
    I'm an American. I love this country and the freedoms that we used to have.
    1. Re:somewhat OT isotope question by forii · · Score: 3, Informative

      Deuterium has different hydrogen bonding properties from H-1. This is a problem because a lot of biology (DNA, for instance) relies on hydrogen bonding to hold things together correctly. If you started drinking a lot of D2O, the differently shaped molecules wouldn't fit together correctly and you would begin breaking down at the cellular level. If I recall correctly the effects are a lot like radiation poisoning.

      Another way that D2O differs from regular H2O.

    2. Re:somewhat OT isotope question by jakobk · · Score: 1

      It reacts a little slower than normal water, enough so that it throws some life processes off.

    3. Re:somewhat OT isotope question by Idarubicin · · Score: 2, Informative
      ...If you started drinking a lot of D2O, the differently shaped molecules wouldn't fit together correctly and you would begin breaking down at the cellular level...

      No! Deuterium behaves chemically exactly like hydrogen-1 (protium) in the compounds that it forms. The physical properties are slightly different (heavy water--deuterium oxide--is denser, and has higher freezing and boiling points. Heavy water ice cubes will sink in a glass of regular water.) Problems arise simply because of its added mass. It's chemical kinetics are different--reactions involving deuterium run more slowly than reactions involving protium.

      In the delicately balanced biochemical environment of the body, this slight slowing of reactions by the involvement of a heavier isotope would likely cause unpleasant symptoms. This has never been tested (to my knowledge) in any system larger than a cell culture. In those cases, replacement of roughly half the light water with heavy water prevented the formation of microtubules, blocking cell division.

      Heavy water costs about three hundred U.S. dollars per liter--so poisoning a human being by this technique would be extremely costly. Not only that, the effect would be reversible with consumption of regular water. The effects would be like radiation poisoning or chemo, because rapidly dividing cells (in hair follicles, digestive tract, bone marrow) would be affected first.

      --
      ~Idarubicin
    4. Re:somewhat OT isotope question by forii · · Score: 1

      No! Deuterium behaves chemically exactly like hydrogen-1 (protium) in the compounds that it forms.

      Did I say anything of the sort? I said that the hydrogen bonding properties are different, and they are, because of the added mass. Hence the change in chemical kinetics that you describe.

    5. Re:somewhat OT isotope question by Muhammar · · Score: 1

      It is slightly incorrect what you said. It is not about different shapes and probably also not about non-covalent, hydrogen bonds. (Acidic H+ get exchanged quickly).

      The problem is that some reaction have large "kinetic isotope effect", which usualy means - in case of deuterium-exchanged molecules - that heavy isotope carbon-deuterium bonds are metabolised at slower rate. Enzymatic reaction do this alot. Oxygen and carbon are other examples - although the effect is not as large as with hydrogen.

      Living organisms have tendency to take up disproportionaly more of lighter isotopes. This can be used to determine, if - for example - limestone sediment rocks or carbon particles had a biotic origin.

      --
      I doubt that we will ever figure out - and I suspect that even if we did figure out we couldn't do much about it
    6. Re:somewhat OT isotope question by JoeRobe · · Score: 1

      Just following up, the kinetic isotope effect is a consequence of differences in activation energies that are due to differences zero-point energies of stable and transition states. These differences in zero-point energies are a result of the effects of isotopic substitution.

      --
      The best way to predict the future is to invent it.
    7. Re:somewhat OT isotope question by gnalle · · Score: 1
      Hmm I am a little confused about your post. From a classical calculation, I would believe that the chance of being at the transition state is independent of mass.

      p(x) = exp(-U(x)/k_BT))

      However the reaction rate is also proportional to the average velocity, which again is proportional to sqrt(m k_B T). Here m is some suitable mass, which will depend on the isotopes.

    8. Re:somewhat OT isotope question by JoeRobe · · Score: 1

      You are correct, except you need to take into account the idea of a zero point energy.

      Specifically, what is U(x)?

      In chemical kinetics U(x), or more properly (delta)U(x) is the energy difference between the stable state and the transition state. When a lighter isotope is substituted with a heavier isotope, the zero point vibrational energy levels all lower in energy. The same thing occurs for the transition state, except that the energy drops less in the transition state. This results in a higher effective reaction barrier, thereby slowing the reaction down.

      Does that answer the question?

      --
      The best way to predict the future is to invent it.
    9. Re:somewhat OT isotope question by gnalle · · Score: 1
      Thanks for your answer. At body temperature I would guess that it was sufficient to use a classical calculation. If this is not true, then I would like to see a reference, so that I can learn :) Here is what I meant to write: In a classical approximation the energy is given by

      E = U(x) + T(p)

      Here x denotes positions of nuclei, whereas p denotes momenta of nuclei. The kinetic energy T(p) is dependent on masses. whereas U is the potential energy denotes the electronic ground state with fixed nuclei at positions x. Thus U is independent of the masses of the nuclei. If we let x_m denote the minimum and x_t denote the transistion state then delta U = U(x_t) - U(x_m) is also independent of the masses.

      At somewhat low temperature we can perform second order expansions of potential energy around the minimum and the saddle point. I don't remember this stuff completely, but from simple analysys of units I would guess that the result is somewhat similar for the two isotopes.

    10. Re:somewhat OT isotope question by JoeRobe · · Score: 1

      Even at body temperature, the molecules are in their lowest vibrational states. Using the U(x) and T(p) terminology, you're right that U(x) will not be affected by changes in mass. However, T(p), specifically, the vibrational energy levels will be affected by the change in mass. Specifically, they will all drop, but the transition state (or saddle point) energies will drop less than those of the stable state, making the effective barrier along the reaction coordinate larger upon substitution. This larger barrier thereby lowers the reaction rate.

      The T(p) is the crucial part of this, and is dependent upon the energy levels occupied. At body temperature, the energy levels occupied are the lowest vibrational levels (and millions of rotational levels of course). Since the Boltzmann distribution depends upon the overall energy of the molecule E, not just U(x), a change in mass affects T(p) which then affects E.

      Does that make sense?

      This info is coming from a book called "The Tunnel Effect In Chemistry" (I forget the author's name), and it is discussed in chapter 4.

      Incidentally, the tunnel effect (which is undoubtedly affected by mass) also plays a role in reaction rates. This is discussed in the second half of the chapter.

      This is a great discussion by the way (this is the reason why I ever post on /.)

      --
      The best way to predict the future is to invent it.
  24. caught on tape by Tablizer · · Score: 1

    Are you the heaviest stable element?

    "None of your fricken bismuth!"

  25. Every element unstable if you wait long enough by Tablizer · · Score: 1, Informative

    Since nobody knows how long even simple elements will last, it is all a matter of degree. Some things decay fast, and some really really really slow, beyond our level of detection. If there is any element that is stable forever, we probably cannot test that since the Universe likely won't last forever according to current theories.

    Thus, "stable" is probably not really a Boolean thing.

  26. ruined! by Tablizer · · Score: 0, Redundant

    "Hector, you drank my experiment! Now I will never know its half-life!"

    "Sorry, Dr. Lanse, but my stomach was really upset."

  27. thallium oxide by n2kra · · Score: 1
    bismuth-209 decays into thallium-205

    Oh, no! The Pak will take over! ... eventually

  28. Heavy water toxicity by CERDIP · · Score: 2, Informative

    Heavy water poisoning of animals is caused by the D2O (heavy water) inhibiting cell division (mitosis). Bacteria growth rates are reduced, leading to problems in the GI tract, and bone marrow activity is reduced. So GI infections and enemia are symptoms. You would need to approach about from about a quarter to about a third of your body weight in D2O to achieve toxic levels. It would cost in the vicinity of $10,000 dollars and you would weight several pounds more when you died.

    --
    ---- ---- --- -- --- ------ Keep Cool But Do Not Freeze
  29. they already knew about this by EddWo · · Score: 2, Funny

    looks like the pepto-bismol people already knew about this

    http://www.pepto-bismol.com/faqs.htm#8

    How do I read the expiration Date? Can I use Pepto-Bismol® past the expiration date?
    Expiration date example:
    EXP JL02C0041
    EXP = expires
    JL = indicates the month (July)
    02 = indicates the last digits of the year (2002)
    C0041 = indicates plant and production information

    If your Pepto-Bismol® has expired, please do not use it. The ingredients may not be stable after the expiration date.

    that would be EXP JL20000000000000002003C0041 I suppose, it should be safe to drink for a while yet.

    --
    "Taligent is still pure vapor. Maybe they'll be the last who jumps up on Openstep... "
  30. Re:It's dangerous? KILL IT!!! by Alsee · · Score: 2, Funny

    that's just an average... It could decay all at once just after you swallow

    True, you're far more likely to have the hydrogen atoms in a glass of water spontaneously fuse after you drank it. If the bismuth decayed all at once it would kill you, but if hydrogen fused all at once it would kill everyone in a 50 mile radius. :)

    -

    --
    - - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
  31. Freedonian by jefu · · Score: 1
    Perhaps "Freedonian" would be better - though it isn't quite "Freedom" and doesn't quite follow the usual naming convention ("ium"). Its a bit more pronounceable and rather more euphonious.

    But best of all, it not only swats those durn Freedomch types, it commemerates the great citizens of Freedonia, ever fighting for their country - led by the most excellent Rufus T. Firefly, and Mrs. Teasdale.

    And in time of war never forget the immortal words of President Firefly :
    "And remember while you're out there risking life and limb through shot and shell, we'll be in here thinking what a sucker you are."

    Hail, Hail Freedonia! Land of the Brave and Free!

  32. Re:It's dangerous? KILL IT!!! by Muhammar · · Score: 1

    Also, do not drink orange juice or eat bananas: these foods are rich in potassium. Naturaly occuring potassium has a lot (several %) of radioisotope. Its beta radiation is soft and decay slow, but the generated heat is enough to keep the Earth molten inside.

    So, fruits are bad - fruits are radioactive. I knew it instinctively since my childhood.

    --
    I doubt that we will ever figure out - and I suspect that even if we did figure out we couldn't do much about it
  33. Are any isotopes of any element stable? by skybird0 · · Score: 1

    If proton decay occurs, then it is unlikey (albeit possible) that any atoms are truly stable.

    1. Re:Are any isotopes of any element stable? by JoeRobe · · Score: 1

      Not necessarily true (I know, hence your albeit)...free neutrons have a halflife of about 15 minutes. The only thing that keeps them stable is interactions within the nucleus.

      --
      The best way to predict the future is to invent it.
    2. Re:Are any isotopes of any element stable? by gumbi+west · · Score: 1

      Good point. You may care to know that the Department of Energy has the the halflife of free neutrons is about 10 minutes 15 seconds.

      They have not changed Bi-209's page yet. I think it will take them some time.

  34. I thought this was old news! by MillionthMonkey · · Score: 2, Informative

    My dad had a copy of Lange's Handbook of Chemistry that was published back in the sixties. I distinctly remember seeing that it listed the half life of Bi-209 as 2x10^23 years. That was only four orders of magnitude too long.

    In principle there are no stable nuclei heavier than iron 56. If you have a nucleus with atomic number A and atomic weight X, and you add up the binding energy of that nucleus, and compare it to the sum of the binding energies of an alpha particle and of a daughter nucleus with atomic number A-2 and atomic weight X-4, you will find that alpha decay is at least a little energetically favorable for many nuclei heavier than iron.

    If alpha decay is energetically favorable for a nucleus, then that nucleus is not stable. Alpha decay is a barrier tunneling process. If there's a potential energy drop on the other side of the barrier, the barrier will get tunneled through by an enterprising alpha particle eventually. It's just a matter of how long it will take- which is determined by the barrier width and the magnitude of the potential energy difference. The only reason many elements (iodine, gold, mercury, lead, etc.) are considered stable by human beings is that their decays have never been observed- because they are difficult to observe within human time scales. You might have to set up your experiment and wait for years, maybe centuries, before you see a decay. A bottle of mercury might contain two alpha decays per century. Is mercury stable? Not really, but for all practical purposes it is. It's all in the eye of the beholder.

    So it seems someone has caught bismuth in the act. Does this mean lead is now the heaviest stable nucleus? No, absolutely not. Lead has some advantages over bismuth- even numbers of neutrons and protons, etc. Pb-208 will definitely have a longer half life than Bi-209. Determining the half life of Pb 208 is going to be hard. But quantitative differences aside, the only real difference between lead and bismuth is that bismuth got caught!

    1. Re:I thought this was old news! by kitty_goth · · Score: 1

      > Pb-208 will definitely have a longer half life than Bi-209. Determining the half life of Pb 208 is going to be hard.

      http://education.jlab.org/itselemental/iso083.ht ml

  35. Drug expiration dates by MillionthMonkey · · Score: 1

    People think expiration dates on medicines are like the dates you see on milk. When milk passes its expiration date, it is bad, period. I used to work in a generic pharmaceutical company under the domain of the FDA. After working in that lab, I lost all respect for expiration dates on pharmaceuticals. I almost never throw away medicine just because it's expired. This is what an expiration date really means:

    A sample is kept from each lot of a drug that's shipped. It's put in a box and kept in a closet somewhere at the drug company. This is mandated by the FDA. Once every three months, someone goes into the closet, takes some out, performs an assay (for bismuth or whatever), and makes sure the stuff still contains between 90% and 110% of the label claim for its active ingredient. They keep doing this until the expiration date passes. Once it hits the expiration date, they're allowed to go into that closet and throw the stuff away. The testing protocol may vary from product to product but the idea is the same. If a bottle of medicine has expired, all it means is that nobody is doing periodic tests on that lot anymore. For most drugs, the assay percentage will remain stable forever afterwards. A few will decay over time. Pepto-Bismol is certainly OK to use unless the pink sugary crap it's in looks or smells suspicious, or if 10^19 years have passed by (don't use Pepto-Bismol that old because it contains thallium).

    We sold a generic version of Pepto-Bismol at this company. They called it "Pink Bismuth". (They were real creative with their ripoff names- "Miconazole 7" for "Monistat 7", "Vision Vite" for "Opti-Vite", etc.) I remember doing some raw material tests and assays on the active ingredient, bismuth subgallate. It's an off-white powder. If I had only known it was radioactive...

  36. bismuth is NOT radioaktive by anythings-possible-b · · Score: 0

    hi!
    i do'nna believe it. nobody is going to cool bismuth to under 40mK. so ...
    at room-temperature is it IS complitely stabil.
    -
    think:
    uranium compressed or plutonium or something else goes critical mass.

    if you cool stuff, their atoms move together.
    maybe the universall laws don't follow MATTER, but geometrie?
    so bismuth IS radioaktiv IF cool below a certain temperature ... so cool(!) their is a critical temperature (like there is a critical masse), but this is nowhere mentioned in the science-page ...
    and one can cool less then 0 Kelvin, but one cannot messure it ...

  37. Unintended Consequences by Detritus · · Score: 1

    I wonder how many laws and regulations will be triggered by the fact that Bismuth is now a "radioactive material".

    --
    Mea navis aericumbens anguillis abundat
  38. how do they know? by u19925 · · Score: 1

    since Bismuth decay rate is the slowest that has been observed, how do they know that other stable isotopes are not so stable? if they don't, then how do they claim that Bismuth is not the heaviest stable element. I guess, the only sure heaviest element would then turn out to be Hydrogen-1 isotope.

  39. How does this relate to naturally formed Bi? by Stonan · · Score: 1

    I have a few 'chunks' of it in my crystal/rock collection. I happen to think it's a cool looking element - continuous geometricly layered squares with oil-like coloring... I've had the pieces for ages but I haven't looked at the collection in at least a couple years. Guess I better check if it's still there!

    --
    The GEEK shall inherit the earth...
    1. Re:How does this relate to naturally formed Bi? by Anonymous Coward · · Score: 0

      those crystals are man made... Bi does not naturally occur on its own in nature. it's always mixed with something else.

    2. Re:How does this relate to naturally formed Bi? by Stonan · · Score: 1

      So is Bi a creation from two or more other elements or is it a by-product? (Sorry for the Mr. Wizard questions)

      --
      The GEEK shall inherit the earth...