Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why # of protons behave this way

  1. Oct 19, 2012 #1
    What makes the number of protons in a atom behave in a certain way to create elements?

    ( It is almost as if there is an underlying computer code to the universe )
    eg:

    100 bhr if 1 proton goto line 1252
    101 bhr if 2 proton goto line 1376
    ~~
    ~~
    1252 prop = very explosive, goto line 3512 solid
    1376 prop = make your voice sound like a chipmunk, goto line 4678 solid
     
  2. jcsd
  3. Oct 19, 2012 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Have you never taken a chemistry course? It's not the protons that "create" elements, it is the electrons. Electrons, and their position in electron shells determine the chemical properties which are what differentiate elements. Of course, an atom is electrically neutral so there must be the same number of protons as neutrons- but it is the electrons that determine the element, not the protons in the nucleus.
     
  4. Oct 19, 2012 #3
    It cant be the electrons, its the protons, because if you were to ionize any element it will still behave the same way, but with a positive charge.
     
  5. Oct 19, 2012 #4

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    Start by indexing possible nuclei by their numbers of protons and their numbers of neutrons. Just forget the names for now. Call each one a "distinct element" [itex]X^p_n[/itex]. For example [itex] X^6_8 [/itex] means the element with six protons and 8 neutrons (we usually call this carbon-14 ...).

    Now you have two issues. How well does the nucleus hold together, and if it does this well enough how does the element behave otherwise.

    To get into nuclear stability you will have to consider the nature of the strong nuclear force binding it together and the fact that the proton's being all positive want to fly apart. This is a deep subject invoking many topics in quantum mechanics and the standard model. But in the end we can roughly say that nuclei with equal numbers of protons and neutrons are somewhat more stable.

    Now you look at the more or less stable cases, the ones that stick around long enough to study. These will have very concentrated positive charges and so will attract electrons. They will keep attracting electrons until you have as many electrons as protons and the atom becomes neutral. However the electrons don't fall all the way into the nucleus. Since the electrons are very very VERY light relative to protons and neutrons they tend to float around in orbits moving very fast. Again this has to do with quantum theory and the fact that the wavelength of the electrons is much bigger than the size of the nucleus when the electrons energy is small enough to be close to the nucleus. There's a trade-off making it very improbable for the electron to "fall all the way in" (and this affects stability of the nucleus since the electron can occasionally hit the proton and make a neutron plus a neutrino).

    So when you study the ways electrons can configure themselves around the nucleus you get (again due to quantum theory) some "resonant" orbital modes. You also have the statistical behavior of electrons as fermions and their mutual repulsion so that they fill up the space around the nucleus in layers that get rather complicated.

    Then we look at how two elements with their clouds of electrons behave together. We find they can form bonds and the bonding behavior is purely a function of the electron configurations. So elements with the same number of protons behave the same way chemically. Elements [itex]X^6_6, X^6_7[/itex], and [itex]X^6_8[/itex] all behave almost identically chemically, so much so that you can eat sugar made of each and not notice the difference (too much). (Their atomic masses differ which affects some reaction and diffusion rates.) (also [itex] X^6_8[/itex] is a bit unstable, having a 50-50 change of exploding every 5730 years and there are a very very large number of them are in a gram of sugar, enough that you'll eventually die of the radiation from the few which are exploding each second if you ate a gram of sugar made of pure C-14.)

    So we, especially not having discovered the nuclear structure yet, decided to give classes of these elements names based on their chemical behavior (tendency to stick together) which we now know is due, indirectly, to the number of protons they have. Atoms with 6 protons we call Carbon. Atoms with 8 protons we call Oxygen. etc. When we look closely enough to distinguish beyond chemical behavior, the number of neutrons we append the total number p+n since we can best indicate the case by the total mass per atom (and protons and neutrons are almost identical in mass.)

    Now if you want to understand why the number of electrons in orbit affects the chemistry in such an odd fashion, creating sometimes metals, sometimes halides, sometimes semiconductors, and sometimes inert gasses, you'll have to master a good deal of mathematics and then the physics of quantum mechanics which uses that mathematics as its language. It isn't too hard but it will take some years. You can begin to understand the "why" of that "computer code" you made reference to.
     
  6. Oct 19, 2012 #5

    Borek

    User Avatar

    Staff: Mentor

    Nope. Metallic sodium behaves very differently than Na+ cation does.
     
  7. Oct 19, 2012 #6
    Yes, but identity is determined by protons. It says so in every textbook that I know of.

    Isotopes differ in neutrons. Electron configuration (which is chemistry, in most respects) generates ions. An H+ ion is still hydrogen after all. Heck, deuterium and tritium are still hydrogen, their just given names because hydrogen is such a common and important element.
     
  8. Oct 19, 2012 #7
    ...this ...isn't correct, somehow.
    Everyone says not to think of electrons as "orbiting" the nucleus, for one thing (at least they do now. When I was in HS still [back in the late 80's], they did talk about orbits, but even then that language was being removed).

    You mentioned quantum mechanics in your next sentence, so I kinda know where you're going, and that I'm basically saying what you already know, but...

    We're not supposed to think of electrons as anything physical any longer, from what I'm getting out of current textbooks. Electrons are just energy, more or less (since we're being really simplistic).
     
  9. Oct 19, 2012 #8
    That is not relevant to the question of chemical properties. Chemical properties are determined by electronic configuration alone.

    Also how do you *detect* atoms and different nuclei? Something for you to think about. Ok something has 1 less proton. PROVE IT with an experiment?
     
  10. Oct 19, 2012 #9
    Right, electron configuration determines chemical properties. That's what I said right there in the quote...

    I'm not sure what you're saying "That is not relevant to the question of chemical properties." to. What "That" are you referring to, here?

    Anyway, how do you detect atoms and different nuclei? I'm not sure that I understand the relevance of this question. The ancient Greeks detected this (without realizing it, of course) by separating things until the properties of the materials that they were separating became immutable. With the right equipment we can detect protons directly these days, though.
    Something with 1 less proton will have a large mass difference compared to the reference matter, so if you stick a mix of the reference stuff with the stuff containing 1 less proton in it into a centrifuge then the stuff with 1 less proton will end up on top. Theoretically you could then skim (most of) that stuff off of the top.
     
  11. Oct 19, 2012 #10
    You cannot detect a single proton. Not in the way you think you can. The point is, you know the identity of an element mostly through its properties in the condensed phase and through its reactions. For those purposes only the electron configuration is important and the nuclei are irrelevant except as centers of positive charge.
     
  12. Oct 20, 2012 #11
    Agreed... I'm not sure what that has to do with the topic, though. The OP was wondering about the reasons why identity is determined by protons, which seems a sensible question to me.
     
  13. Oct 21, 2012 #12

    jambaugh

    User Avatar
    Science Advisor
    Gold Member

    Yes I oversimplified quite a bit. Otherwise I'd have a post three times longer. BTW we generalize the term "orbit" to mean the generic dynamic evolution, whether that be a classical elliptical orbit of a point mass around a center or whether it is the time evolving wave function. The electron as a quantum phenomenon when "ïn a bound orbit" is in a superposition of the stationary standing wave solutions to its dynamical equation... or rather the wave-function we utilize to describe our knowledge about its likely observable behavior is.

    We could then get hung up in interpretational debates over whether the wave-function is physical or representational and loose sight of the main point... that the number of protons dictates the structure of "orbiting" electrons which dictates the chemical properties.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Why # of protons behave this way
  1. Why protons dissociate (Replies: 6)

Loading...