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Stable Ions

  1. Sep 6, 2017 #1
    Hello,
    I have been wondering if it is possible to create and store stable ions, is it?
    Thanks.
     
  2. jcsd
  3. Sep 6, 2017 #2

    Borek

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    Define "create and store".

    I have a bag of kitchen salt, it is made of ions, they are all stable. Not that I made it by myself, but need be, I know how to.
     
  4. Sep 6, 2017 #3
    By create I mean make or produce. By store I mean keep the stable ions in a jar or something.
    In my original question I also mean free particles with a negative or positive charge, not in a compound, like NaCl, but rather like Na+ or Cl- independent of each other.
     
  5. Sep 6, 2017 #4

    Borek

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    Basic chemistry or basic physics. Process is called ionization.

    So you want to separate them. Not trivial, but definitely doable: https://en.wikipedia.org/wiki/Ion_trap

    Do you know what coulomb forces are? Try to estimate force with which one mole of Na+ attracts one mole of Cl-, assuming they are separated by 1 meter distance. Compare this number with the force keeping Moon in the Earth orbit. Do you see a problem?
     
  6. Sep 6, 2017 #5
    What if we separate the ions with a wall?
     
  7. Sep 6, 2017 #6

    Borek

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    Wall doesn't block electric field.

    How you ever played with magnets? Do they attract each other through wood, paper? Charges are very similar.

    Things get a bit more complicated when we try to separate charges with something conducting, but the attraction will be still there.
     
  8. Sep 6, 2017 #7
    So, you mean that the electrons can still pass through the material separating the ions? Could I instead use a non-conducting wall?
     
  9. Sep 6, 2017 #8

    Borek

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    Attraction is not because of the electrons moving, but because of the existing electric field, created by separated charges.

    Have you tried to estimate forces I told you about earlier? That will be a very interesting exercise, if you really want to learn something - do it.
     
  10. Sep 6, 2017 #9
    Could you check my process and math, please?
    These are my steps:
    E=F/q
    where q is the quantity of charge and E is the electric field strength.
    F=k x q x Q/d2
    where Q is the electric charge and k is the constant of k=9.0 x 109
    So, from these formulas we derive the formula for the electric force to be:
    E=kQ/d2
    Then we plug our numbers in to get:
    E=9.0 x 109x(-1)/12=9,000,000,000x(-1)/12=-9,000,000,000/1=9x109.
    So, we have calculated the electric field strength of one negative ion of chlorine (or basically any atom with charge of -1).
    Could you please check my working?
    Do you understand this or do you want me to explain myself a bit more?
    Thank you very much.

    P.S. I got this information from: http://www.physicsclassroom.com/class/estatics/Lesson-4/Electric-Field-Intensity

    Ivan.
     
  11. Sep 6, 2017 #10

    Borek

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    That's already formula for calculating force, no need to do anything more, just plug the numbers.

    But - beware of the units! The charge must be expressed in coulombs. Before plugging anything into the equation find out (google will help enormously) what is a charge of an electron expressed in coulombs.

    Then, you have to find out what units is the calculated force in. It is like with a distance - if I tell you that the distance between my chair and my car is 30 you will not know if it is 30 inches, 30 feet, or 30 miles, so such information is useless. Page you linked to contains the information about units of the constant k - and you will need these units to calculate the force.
     
  12. Sep 6, 2017 #11
    What is the difference between the source charge and the test charge from the website?
    Should I measure the F in Newtons?
     
  13. Sep 6, 2017 #12

    Borek

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    Technically no difference at all. We sometimes think in terms of source charge being a large, immobile one in the center of the system, and the other charge being small and used to measure the force with which it is attracted (or repelled), but it is purely conventional which one is which. You have two charges, that's all what matters.

    Makes sense (and will be the easiest thing to do here), but nothing stops you from using any other force unit - as long as you clearly state what you used.

    But yes, stick with newtons for now.
     
  14. Sep 8, 2017 #13

    DrDu

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    I just wanted to note that free ions are routinely stored and handled in particle accelerators and cyclotrons. This is also used analytically, e.g. in ion cyclotron resonance mass spectroscopy.
     
  15. Sep 8, 2017 #14
    True, but how do they get made in the first place? With what chemical reaction?
     
  16. Sep 8, 2017 #15

    DrDu

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    Usually, you generate these ions not in a chemical reaction but bombarding a dilute gas with e.g. electrons, which leads to ionisation.
     
  17. Sep 8, 2017 #16

    DrDu

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  18. Sep 8, 2017 #17
  19. Sep 8, 2017 #18

    Borek

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    Yes, you need strong electric fields to make the electrons fast enough on a relatively short distance.
     
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