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Thread: The atom's stable configuration

  1. #1 The atom's stable configuration 
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    Hi,
    I am new member of this forum, and I have one question for you. When the atom have 8 electrons in the last shell, why it have stable configuration? What makes the atom to be stable and what makes the atom to be reactive?
    Best regards.


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  3. #2  
    Forum Professor river_rat's Avatar
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    Its called the octet rule (of thumb).

    Wiki to the rescue - http://en.wikipedia.org/wiki/Octet_rule


    As is often the case with technical subjects we are presented with an unfortunate choice: an explanation that is accurate but incomprehensible, or comprehensible but wrong.
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    Forum Senior anand_kapadia's Avatar
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    Hey you can't ask that if it is computer so how it is.
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  5. #4 Re: The atom's stable configuration 
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    Quote Originally Posted by scientist91
    Hi,
    I am new member of this forum, and I have one question for you. When the atom have 8 electrons in the last shell, why it have stable configuration? What makes the atom to be stable and what makes the atom to be reactive?
    Best regards.
    Hey, and what I'd like to know is what is the difference between an atom becoming reactive and radioactive?

    And what causes an atom to become unstable/radioactive?
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  6. #5  
    Red
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    Atoms become radiactive when they have too much energy in their nucleus. This instability is usually caused by having an unnatural ratio of neutrons to protons. They have to emit this energy to become stable again so they either emit mass from their nucleus as in alpha or beta radiation or electromagnetic photons as in gamma radiation. These energies can in themselves cause radioactivity by adding themselves to other atoms messing up their composition. Thats why exposure to radiation can in some cases cause materials to also become radioactive
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  7. #6  
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    Quote Originally Posted by Red
    Atoms become radiactive when they have too much energy in their nucleus. This instability is usually caused by having an unnatural ratio of neutrons to protons. They have to emit this energy to become stable again so they either emit mass from their nucleus as in alpha or beta radiation or electromagnetic photons as in gamma radiation. These energies can in themselves cause radioactivity by adding themselves to other atoms messing up their composition. Thats why exposure to radiation can in some cases cause materials to also become radioactive
    Why the stability depends from the energy? What is the role of the energy?
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  8. #7  
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    Short answer I dont know there just seems to be a certain mass and energy that an atom has before it becomes unstable you should look up the internet for the deep reaons behind it
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    Quote Originally Posted by Red
    Short answer I dont know there just seems to be a certain mass and energy that an atom has before it becomes unstable you should look up the internet for the deep reaons behind it
    So you say that the nucleus excites the 2s electron to go in the 2pz orbital right?
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  10. #9  
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    Quote Originally Posted by Red
    Atoms become radiactive when they have too much energy in their nucleus. This instability is usually caused by having an unnatural ratio of neutrons to protons. They have to emit this energy to become stable again so they either emit mass from their nucleus as in alpha or beta radiation
    They say that tritium(hydrogen-3), because it has one proton and two neutrons, is unstable. To become stable it needs to decay into helium-3. However, 'decay' seems kind of a strange choice in words because the end result of the decay is that we go from tritium (1 proton and 2 neutrons) to helium-3 (2 protons and 1 nuetron)

    Are there any theories about what happens to the nucleus of an unstable atom as it decays? For instance, does the neutron gradually wean away, or is somesort of threshold reached and it just dissappears? And how does the extra proton emerge after a period of decay?

    I guess what I'm asking is, what is the relationship between the extra neutron creating the imbalance, and the alpha and beta waves being radiated?

    I'm kind of visualizing a boiling pot of water, and as the gas leaves the water, the water shrinks away. Ultimately its escaping from the pot in the form of gas. So to use this analogy I ask:

    Does the extra neutron escape from the atom by changing into alpha. beta radiation, or electromagnetic photons as in gamma radiation - much like water escapes from the pot by changing into gas?


    These energies can in themselves cause radioactivity by adding themselves to other atoms messing up their composition.
    This I don't understand because I though it was only an extra neutron or proton that causes instability. So you think the energies that escape from an unstable atom somehow make their way into other atoms? What form to they take, and how?

    Thats why exposure to radiation can in some cases cause materials to also become radioactive
    hmmm.......it sounds like the nucleus of the atoms exposed gets mutated into an unstable isotope simply by being exposed to the radiation emited by an already unstable material. I would just like to visualize how exactly the intererior of an atom goes through that transformation - from stable to unstable.
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  11. #10  
    WYSIWYG Moderator marnixR's Avatar
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    Quote Originally Posted by Red
    Short answer I dont know there just seems to be a certain mass and energy that an atom has before it becomes unstable you should look up the internet for the deep reaons behind it
    as far as i'm aware the only thing that keeps protons in the nucleus together is the strong nuclear force - after all, even with neutrons in there the repulsive force of the protons should break up the nucleus if there wasn't anything counteracting it

    however, the strong nuclear force may be strong, but its reach is very limited : any nucleus larger than that of lead starts to slip out of its reach, and the larger the nucleus, the more unstable the element

    [edit]
    i must admit this explanation does not hold for light radioactive elements such as tritium
    [/edit]
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  12. #11  
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    Well as they say You learn something everyday and just happens I was delivered the answer today to your question. So basically you have a positive nucleus and these positive protons repel each other. The only way to keep these in such a small close confinement without them tearing away from each other is to have a certain amount of neutrons to dampen the repulsion. The exact cause of this is as yet unknown to me but it is very closely linked to the strong nuclear force that binds the nucleus together. You usually need about an equal number of neutrons from protons to keep the nucleus together for small numbers of protons such as in the helium nucleus but as the atomic number or nuclear charge increase the number of nuetrons required to dampend them increases to over double. If something is decating it is because either there are not enough neutrons for that number of protons so some must be expelled (alpha decay) to form a stable arrangement or there are too many neutrons so a neutron which can be seen as a proton with an embedded electron so accounting for its slightly increased mass and neutral charge reverts to become a seperate proton and electron and the elctron is fired out with great speed (betta decay) or if the imbalance is only a result of the neutron proton arrangement being needed to be reorganised so the neutrons can keep the protons together all that is released is energy in the e.m. spectrum as gamma waves (gamma radiation) Just ignore the simplified version that I previousely knew this is a step forward to the bare facts which if i ever learn i will post. This is what happens when people try and use analogise to describe something rather than the atuall way it happens.

    This balance is very strict and if another balanced nucleus absorbs the energy or mass it can be put out of balance and so beome unstable in itself. It is not changed into an isotope when absorbing mass though but into a complete different element just to answer your question remit.
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    WYSIWYG Moderator marnixR's Avatar
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    also remember that as the atomic number increases, the neutron / proton ratio tends to increase beyond the ideal ratio of 1
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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