Question About Nuclear Decay By Alpha Particle Emission

Discussion in 'Physics' started by Glenn Holland, Jul 7, 2017.

  1. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    My chemistry book describes the radioactive decay of Polonium (Po) into Lead (Pb). The explanation says that two protons and two neutrons (an Alpha particle which is essentially a Helium nucleus) are ejected from the Polonium nucleus and the particle eventually acquires two electrons to form a plain vanilla Helium atom.

    However, the book describes the electron capture as a two step sequence where the Alpha particle is ejected completely from the Polonium atom and acquires two electrons from the "surrounding atoms" (it doesn't say what elements the atoms are) which then become cations. Then the surrounding atoms acquire electrons back from the Polonium and the decay process is complete - game over.

    Seems that the electron capture of the Alpha particle would be done in just one step with the particle just snatching two electrons on its way out of the Polonium atom. Furthermore, what happens if the Polonium atoms are isolated from other elements and can't acquire electrons from the surroundings? That would leave the Polonium atom as a positive ion.
     
  2. crutschow

    Expert

    Mar 14, 2008
    20,017
    5,629
    It may be going too fast to readily capture an electron around the atom on its way out.
    The Polonium (now lead) has too many electrons, so they probably just wander into space if they have no place else to go, since there's now no electrostatic force from the nucleus to keep them in orbit.
     
  3. Papabravo

    Expert

    Feb 24, 2006
    11,703
    2,464
    Quantum Mechanics does not allow us to say which electrons are captured. We cannot fix the positions of any electrons in the original Polonium atom or the Lead atom it becomes. Alpha particles are not very energetic or fast moving. They will capture electrons eventually. Why does it matter where they came from?

    From the wiki
    Due to the mechanism of their production in standard alpha radioactive decay, alpha particles generally have a kinetic energy of about 5 MeV, and a velocity in the vicinity of 5% the speed of light.
     
    killivolt and cmartinez like this.
  4. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    So if there's a large block of decaying Polonium that's completely isolated in a vacuum and the Alpha particles escape (with the electrons), then the space around the lead would have a monstrous blob with a negative charge. If there's one mole of lead (with two free electrons for each atom) and it ever gets near something that has a positive charge, there's going to be a hell of a spark!!! :eek:
     
  5. nsaspook

    AAC Fanatic!

    Aug 27, 2009
    4,798
    5,168
    Yes.
    [​IMG]
    http://homepages.cae.wisc.edu/~blanchar/res/BlanchardKorea.pdf
     
    Motanache likes this.
  6. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    Gee - I wonder If Tesla's going to offer a car with nuclear batteries???

    However, it will be a hell of mess if a nuclear powered car gets totaled in an accident. The whole freeway (and the nearby town) will be closed for months for HazMat clean up!!!:eek:
     
  7. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    Here's an update from a book on this subject.

    It says something to the effect:
    If the largest atom has a diameter of 1 mile, the diameter of the nucleus would be about 2/3 inch. So the volume within the outermost electron orbit would be so enormous that the atom consists of mostly empty space. Furthermore, the velocity of the emitted Alpha particle is about 10,000 miles/second. So it is possible for the Alpha particle to shoot right on through all the orbital shells with a low probability of hitting an electron.

    Reminds me of the WWII machine guns that shoot through the propeller without hitting the blades. Of course the machine gun was synchronized with the engine so it could fire only after a blade passed!!! :p.
     
  8. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    5,509
    6,466
    Two things:
    • To which specific book are you referring to? (I'm interested)
    • Aren't the planes you've mentioned those of WWI instead?
     
  9. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    The book I'm referring to is Chemistry - A Conceptual Approach by Charles E. Mortimer and published in 1971 by D. Van Nostrand & Company.
     
    cmartinez likes this.
  10. Papabravo

    Expert

    Feb 24, 2006
    11,703
    2,464
    The synchronized machine gun showed up in mid 1915(German) and 1917(British). There were quite a few unexpected emergency landings before then.
     
    killivolt, nsaspook and cmartinez like this.
  11. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    5,509
    6,466
    Here's an interesting factoid that you might like:

    From “The Seven Mysteries of Life,” (1978), by Guy Murchie.

    "Recent studies at the Oak Ridge Atomic Research Center have revealed that about 98 percent of all the atoms in a human body are replaced every year. You get a new suit of skin every month and a new liver every six weeks. The lining of your stomach lasts only five days before it's replaced. Even your bones are not the solid, stable, concrete-like things you might have thought them to be: They are undergoing constant change. The bones you have today are different from the bones you had a year ago. Experts in this area of research have concluded that there is a complete, 100 percent turnover of atoms in the body at least every five years. In other words, not one single atom present in your body today was there five years ago."


    Of course, the author could very well be wrong... but it's a statement worth pondering, even after 40 years.
     
  12. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    I wonder if the atoms in brain cells are being replaced at frequent intervals and being exactly duplicated so animals (including humans) don't lose their memory.

    In that case, the DNA must also contain code for the information stored in the old cells, otherwise there'd be a massive outbreak of Alzheimer's disease. :eek:
     
    killivolt likes this.
  13. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    5,509
    6,466
    That's the point of my comment... we're just information! ... it's the atom's arrangement that matters, and not the atoms themselves... I mean, how can you tell one water molecule apart from another?

    On the other hand, the author does concede that our bones might be the exception to the aforesaid observation...
     
  14. WBahn

    Moderator

    Mar 31, 2012
    23,075
    6,929
    Yes and no. Synchronization first occurred fairly early in WWII. Before then some planes mounted the guns on the upper wing, but that was difficult to shoot (remote firing guns weren't around yet, but appears about the same time) and so they would mount steel plats on the backsides of the wooden props to deflect the bullets. Worked for the most part, but a prop can only take so much before it sheds a blade (and often then shakes the engine right out of its mounts). The wings weren't structurally sound enough or rigid enough to serve as a suitable mounting platform even after remote firing mechanisms came along.

    Synchronized firing through the propeller was still around on quite a few aircraft in WWII. The French, British, and American designers switched to in-wing mounted guns, primarily because heavier weight of fire was needed as the natural prey of the fighter shifted to all-metal bombers. Germany, Japan, and the Soviet Union continued to favor fuselage mounted guns, at least as the core of a fighter's armament, throughout the war and, in the Soviet's case, even into the Korean War.
     
  15. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    While we're on the subject of nuclear physics, I'm wondering how neutrons are created in the first place.

    If two hydrogen nuclei that usually don't have any neutrons (except for deuterium or tritium) can be fused into a helium nuclei (which does have two neutrons), how are these neutrons created in the fusion process? Since a neutron has rest mass, then some energy must be derived from the fusion process to create one neutron in accordance with E = mc Squared.

    It is believed that all of the elements beyond hydrogen were formed by the fusion process in stars so that same process must also have created the neutrons present in all elements including those that are radioactive and contain excess neutrons.
     
  16. nsaspook

    AAC Fanatic!

    Aug 27, 2009
    4,798
    5,168
  17. WBahn

    Moderator

    Mar 31, 2012
    23,075
    6,929
    It's not a coincidence that the mass of a neutron is pretty close to the sum of the mass of a proton and an electron.

    So a neutron can decay to a proton and an electron.

    A proton can also capture an electron to become a neutron.

    In a star (and I'm reconstructing this from memory, so I may get the details wrong), two protons fuse to produce a He-2 nuclei (just two protons, no neutrons). This is very unstable and decays to deuterium. Now you have a source of the more commonly known fusion of deuterium into He-4.

    Of course, this is just one of the many possible interactions.
     
    nsaspook and cmartinez like this.
  18. Glenn Holland

    Thread Starter Active Member

    Dec 26, 2014
    589
    289
    I've been giving some thought to this question and I believe a "prompt" Alpha particle (one that's been immediately ejected from the nucleus at an extremely high velocity) must be slowed down to the "thermal velocity" of the surrounding atoms in order for it to capture electrons.

    This is similar to "thermalizing" neutrons in order to increase their probability of being captured by a nucleus in the fission process.
     
    Last edited: Jul 16, 2017
  19. crutschow

    Expert

    Mar 14, 2008
    20,017
    5,629
    A few, such as some versions of the BF-190, had a cannon that fired out of the center of the propellor, the engine being slightly offset from the gun and propellor. That eliminated the need for a synchronizer, of course, and also required no convergence adjustment.
     
    cmartinez likes this.
  20. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    5,509
    6,466
    So you're saying the propeller's shaft was hollow, and that bullets were being fired through it? Very interesting, I wonder why the design didn't become more popular.
     
Loading...