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Thread: Octet Rule and the Orbitals...

  1. #1 Octet Rule and the Orbitals... 
    Jia
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    I'm a bit confused that once we say that the s, p and d orbitals can accommodate 2, 6 and 10 electrons and so on... but then on the other side we state the Octet rule - that an atom is stable when it has 8e` in the outermost shell. So if 8e` are needed, why need the orbitals theory??

    I've always been confused about this... so a little help please...


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    Jia
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    Anyone??? Knock knock!!


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    Quote Originally Posted by Jia View Post
    Anyone??? Knock knock!!
    I have asked myself a similar question My own conclusion is that the most stable atoms have an even number of electrons in the orbitals. For an uneven number of electrons in orbit, the atom would tend to vibrate in space.
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  5. #4  
    Jia
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    that still doesn't answer my question... :/
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  6. #5  
    Jia
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    That still doesn't answer my question... :/
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  7. #6  
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    An atom/ion is generally said to be most stable when it's "s" and "p" sub-shells are filled. Transitional metals are defined by the ability to lose "d" sub-shell electrons to form ions, which is why they often have a number of stable and metastable oxidation states.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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    Quote Originally Posted by Jia View Post
    That still doesn't answer my question... :/
    Well, it partially answers your question since it provides a reason as to why the most stable atoms have an even number of electrons.

    We need an orbital theory to determine just where the electrons are located. If it is an orbital, then the electrons must be located on a sphere or an ellipse. Energy measurements indicate that the electron of the hydrogen atom lies on a sphere of probable diameter. It would be more accurate if the orbits were defined, which is the approach that Neils Bohr utilized. In his model, the orbits increase with size, which we know cannot be true, so his model is abstract (which he admitted). In QM, we have probable orbitals which are not exact.

    Where would you put the electrons?
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    About the octet rules generally any atoms that ends with filled S , P [filling f,d orbit needs much more energy]orbit assumed that follows the octet rules means its willing to react with other atoms significantly decreased -the only way that atoms like to react with each other is to recieve electron or losing the in order to form their orbits as octet one-about the atomic theories the most complete one is orbital theory that as you said assume a space around core which electron may be , if atom are in octet form for each layer the movement of electerons is predictable even in those that have not octet form according to three kind of orbitals [x,y,z] their movement is peredictable but if you mean ,you want to point on somewhere in orbital space say ok right now it should be there we do noot have theory to estimate that because of electron`s constant moving -based on cheos theory it may be
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  10. #9  
    Jia
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    But if the atom is stable by just filling the s and p orbitals, how come some atoms have d and f orbitals as well??
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  11. #10  
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    Because in those cases the energy required for an electron to occupy the d or f orbitals is less than the energy required to occupy the next s or p orbital. Case in point,


    I'm no chemist but i think there's a difference between stable electron configurations and chemical stability of atoms. chemical stability being present in atoms with filled s and p orbitals.
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  12. #11  
    Geo
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    Look at MO Theory. That's Molecular Orbital Theory.
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    Hi, the octate rule is about the valence electrons only so it only counts the outer electons. An atom will fill is orbits with elctrons in this order 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 and i can't remember where exactly f comes in. this is how the atom will fill but you woudn't write in that order. That is because the quantum number n must be place in proceeding order so 1s2 2s2 2p6 3s2 3p6 3d10 4s2. Just incase you don't know n then in 1s2 n=1 so there is the one electron shell (don't confuse shell with orbitals), in 3p6 n=3. Because the octate rule is only concerned with the valence electrons you only want the number of electrons from the highest valued n. So if you have a transition metal like Zinc (Zn which is techniqually speak not a transition metal but it is a transition metal in the periodic table.) Zn= 1s2 2s2 2p6 3s2 3p6 3d10 4s2 so the highest value of n is 4 and there is only 4s2 so only 2 valence electrons. so when calculating valence electrons because of the way electrons are arranged and atoms are filled the d and f orbitals will never count as valence electrons.

    The octate rule goes by 8 because all atoms want to be like nobel gases. Nobel gases won't have 8 electrons but they will always have 8 valence electron (therefore all outer shell orbitals are filled). If you look at the first ionization energy of the noble gases you will see that they all will have a value of about 0 KJ, this value of 0 makes them increadibly stable and also means that they won't give away or gain electrons. This is what makes them stable and why all other atoms want to be like them.

    There are exceptions to the rule, most commonly H which only has 1. Also in some cases the central atom will have more then 8 to accommodate more atoms surrounding it but this very rarely happens and I don't know if it can actually occur naturally but don't worry about it if you have at the most just start chemistry at a university level, the lectures probably won't include any examples like this.
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