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  1. Standard member sonhouse
    Fast and Curious
    15 Dec '15 18:50
    Ruthenium, AMU 44 but it comes in 7 isotopes. 96 Ru, 98 Ru, 99, 100, 101, 102, 104.

    Notice the gap in isotope #'s at the bottom, 96 to 98, no 97 and the top number, 102 and 104, also missing 103.

    Anyone have an idea why the missing isotope #'s?

    This is from a professional journal I get, "Vacuum Technology and coating" Sept. 2015 issue, page 32.
  2. 15 Dec '15 19:35
    It depends on what you mean by "comes in." That list is probably the list of naturally occurring isotopes. The other ones can be synthesized but are not stable long enough to be found in nature. Why are certain isotopes more stable than others? I'm not sure there is a straightforward answer to this (at least not for the specific case of, say, 97-ruthenium versus 96-ruthenium) - atomic nuclei aren't the simplest of systems.
  3. Standard member sonhouse
    Fast and Curious
    15 Dec '15 19:44 / 2 edits
    Originally posted by KazetNagorra
    It depends on what you mean by "comes in." That list is probably the list of naturally occurring isotopes. The other ones can be synthesized but are not stable long enough to be found in nature. Why are certain isotopes more stable than others? I'm not sure there is a straightforward answer to this (at least not for the specific case of, say, 97-ruthenium versus 96-ruthenium) - atomic nuclei aren't the simplest of systems.
    They listed the natural abundance percentage for each, 3 and 4 digit accuracy and they added up to 100% so I take it from those numbers there is no natural 97 or 103. Like you say, it must have something to do with stability issues. Maybe way too radioactive, short half life, something like that.

    Anyone else with an answer?

    Found this on 'chemicool' site:

    Isotopes: Ruthenium has 26 isotopes whose half-lives are known, with mass numbers from 90 to 115. Naturally occurring ruthenium is a mixture of seven isotopes and they are found in the percentages shown: 96Ru (5.5, 98Ru (1.9, 99Ru (12.8, 100Ru (12.6, 101Ru (17.1, 102Ru (31.6, and104Ru (18.6. Naturally, the most common isotope is 102Ru with an abundance of 31.6%.

    26 isotopes! So these 7 are just the natural occurring ones. So there is a 97 and so forth.
    The crazy face icons are RHP's way of showing the percent symbol it looks like.
  4. 15 Dec '15 20:05
    Originally posted by sonhouse
    They listed the natural abundance percentage for each, 3 and 4 digit accuracy and they added up to 100% so I take it from those numbers there is no natural 97 or 103. Like you say, it must have something to do with stability issues. Maybe way too radioactive, short half life, something like that.

    Anyone else with an answer?

    Found this on 'chemicool' ...[text shortened]... 7 and so forth.
    The crazy face icons are RHP's way of showing the percent symbol it looks like.
    Every element has infinity isotopes - the type of element fixes the number of protons and the number of neutrons is arbitrary. Of course, not all of these isotopes are stable (most of them aren't) but there's nothing stopping you from putting a bunch of protons and neutrons together (as long as they're not too close, that is).
  5. Standard member DeepThought
    Losing the Thread
    15 Dec '15 23:40
    Originally posted by sonhouse
    Ruthenium, AMU 44 but it comes in 7 isotopes. 96 Ru, 98 Ru, 99, 100, 101, 102, 104.

    Notice the gap in isotope #'s at the bottom, 96 to 98, no 97 and the top number, 102 and 104, also missing 103.

    Anyone have an idea why the missing isotope #'s?

    This is from a professional journal I get, "Vacuum Technology and coating" Sept. 2015 issue, page 32.
    The missing isotopes are all extremely unstable and rapidly decay into other elements, see the Wikipedia page on ruthenium isotopes [1]. Why the stable isotopes come in those particular relative amounts hangs on the processes that form them. All elements heavier than iron (proton number 26) are formed in endothermic fusion during supernovae (at least that's the theory, with a fair amount of evidence to support it). So during supernovae all sorts of possible elements are produced, most of which are insanely unstable and decay until they decay into stable isotopes. The reason for the differences in abundances depends on the probabilities of the different precursors being formed in the supernova (which depends on neutron capture cross-section) and the different decay routes that end with stable isotopes of ruthenium (rather than something else). Then there's the matter of how different elements become distributed throughout the solar system and throughout the Earth - we only see the distributions in the crust.

    At a hand waving level, we would anticipate that isotopes with an odd number of neutrons would be less stable - as each orbital can admit two neutrons and two protons, providing the protons each have opposite spins and the neutrons do. The proton number is even, so the isotopes with odd mass number are liable to be unstable. This is reflected in the only stable odd atomic mass isotopes being 99 and 101, but there being 5 stable(ish) even mass number isotopes.

    [1] https://en.wikipedia.org/wiki/Isotopes_of_ruthenium
  6. Standard member sonhouse
    Fast and Curious
    16 Dec '15 02:27 / 3 edits
    Originally posted by DeepThought
    The missing isotopes are all extremely unstable and rapidly decay into other elements, see the Wikipedia page on ruthenium isotopes [1]. Why the stable isotopes come in those particular relative amounts hangs on the processes that form them. All elements heavier than iron (proton number 26) are formed in endothermic fusion during supernovae (at least t ...[text shortened]... ble(ish) even mass number isotopes.

    [1] https://en.wikipedia.org/wiki/Isotopes_of_ruthenium
    so would it follow if the proton # is even, the opposite is true?

    When the piece I put up says 26 isotopes, were the rest manufactured in a particle accelerator?

    Wonder why the odd men out, 99 and 101, is stable.
  7. Subscriber AThousandYoung
    Do ya think?
    16 Dec '15 06:10 / 1 edit
  8. Standard member sonhouse
    Fast and Curious
    16 Dec '15 11:06
    Originally posted by AThousandYoung
    Ah, a lesson in the old 'null set' theory, eh
  9. Standard member DeepThought
    Losing the Thread
    16 Dec '15 11:30
    Originally posted by sonhouse
    so would it follow if the proton # is even, the opposite is true?

    When the piece I put up says 26 isotopes, were the rest manufactured in a particle accelerator?

    Wonder why the odd men out, 99 and 101, is stable.
    The most important effect for stability is to have enough neutrons to shield the electric charge of the protons from one another. There is a range of stable isotopes with mass numbers from 96 to 104, with the lowest energy (most stable) per nucleon probably for mass number 100. As one moves away from that the energy per nucleon increases. The penalty for having an odd neutron is not enough to make the elements with mass number 99 and 101 unstable, but the combined effect of insufficient shielding (or too many neutrons and consequent beta decay) and asymmetry is too big for mass numbers 97 and 103.

    They're probably created by neutron bombardment of stable isotopes of either Ruthenium or lighter elements in a nuclear reactor.
  10. Standard member sonhouse
    Fast and Curious
    16 Dec '15 12:27 / 2 edits
    Originally posted by DeepThought
    The most important effect for stability is to have enough neutrons to shield the electric charge of the protons from one another. There is a range of stable isotopes with mass numbers from 96 to 104, with the lowest energy (most stable) per nucleon probably for mass number 100. As one moves away from that the energy per nucleon increases. The penalty ...[text shortened]... ron bombardment of stable isotopes of either Ruthenium or lighter elements in a nuclear reactor.
    This shielding effect of neutrons, does that happen just because the neutron is taking up space, basically separating protons from one another, that keeps the proton charges apart?

    In all my years as an Ion Implanter specialist, it accelerates ions, some in the multi megavolt range, mine up to a half meg. I was too involved with the physics of the machine and the effects of isotopes on the flight path of the ion beam, for instance, using a mass analysis ion separator that would allow us to choose which ion got accelerated, like Boron 11 instead of Boron 10 since 11 is about 3 times more abundant than 10, the 11 isotope simply made for a beam 3 times more intense and therefore 1/3 the time needed to make conductive layers under the surface of our silicon wafers and other substrates.

    I was focused on that technology and never really studied these esoteric effects.

    Thanks for showing me some of the details. Just looking at the Wiki piece on Ruthenium shows just how complex even ONE element actually is internally.
    Mindboggling actually.
  11. 16 Dec '15 13:07 / 1 edit
    Interesting article:
    http://chemwiki.ucdavis.edu/Physical_Chemistry/Nuclear_Chemistry/Nuclear_Stability_and_Magic_Numbers

    Also see charts here:
    https://en.wikipedia.org/wiki/Nuclide#Nuclear_properties_and_stability
    and here:
    https://en.wikipedia.org/wiki/Stable_nuclide
  12. Standard member sonhouse
    Fast and Curious
    16 Dec '15 13:10 / 1 edit
    Originally posted by twhitehead
    Interesting article:
    http://chemwiki.ucdavis.edu/Physical_Chemistry/Nuclear_Chemistry/Nuclear_Stability_and_Magic_Numbers
    So the 'job' of neutrons is to shield proton charges from one another.

    Can there be stable atoms with just two protons? no neutrons?

    Why do the charges need to be shielded from each other in the first place? They are like charges so they would be in no danger of crashing into each other, self repelling. Why do they need neutrons then?
  13. 16 Dec '15 13:19
    Originally posted by sonhouse
    Can there be stable atoms with just two protons? no neutrons?
    No. It exists but is very unstable:
    https://en.wikipedia.org/wiki/Isotopes_of_helium#Helium-2_.28diproton.29

    Why do the charges need to be shielded from each other in the first place? They are like charges so they would be in no danger of crashing into each other, self repelling. Why do they need neutrons then?
    There are two forces at play. One is attractive and is universal to protons and neutrons. The other is repulsive and applies only to protons. If you want more attraction than repulsion you need to add more neutrons. At least that's the simple answer. I am not qualified to give the complicated answer.
  14. Standard member sonhouse
    Fast and Curious
    16 Dec '15 13:34
    Originally posted by twhitehead
    No. It exists but is very unstable:
    https://en.wikipedia.org/wiki/Isotopes_of_helium#Helium-2_.28diproton.29

    [b]Why do the charges need to be shielded from each other in the first place? They are like charges so they would be in no danger of crashing into each other, self repelling. Why do they need neutrons then?

    There are two forces at play. On ...[text shortened]... neutrons. At least that's the simple answer. I am not qualified to give the complicated answer.[/b]
    Here is another site giving explanations of proton-neutron interactions:

    http://www.sjsu.edu/faculty/watkins/neutronrepulsion.htm
  15. 16 Dec '15 14:04
    Originally posted by sonhouse
    Here is another site giving explanations of proton-neutron interactions:

    http://www.sjsu.edu/faculty/watkins/neutronrepulsion.htm
    That appears not to be authoritative though.

    And what's with the horrible colour scheme?