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Thread: Compounds formed by three atoms

  1. #1 Compounds formed by three atoms 
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    The mathematical method to create compounds of two atoms is known to all of us
    E.g. Na2O Sodium valency 1, oxygen 2, criss-cross the valencies to obtain Na2O.
    So what is the similar procedure for creating compounds with three different atoms
    E.g. Na2ZnO2?

    Thanks and regards
    Ashwin


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  3. #2  
    Bullshit Intolerant PhDemon's Avatar
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    You might find this link useful Oxidation State - Chemwiki


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  4. #3  
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    Well, I know about oxidation number(state) but can you explain it to me in this particular case?

    Thanks
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  5. #4  
    Bullshit Intolerant PhDemon's Avatar
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    I'm not sure exactly what you are asking... but in the compound you have given, following the rules in the link I gave, the sum of the oxidation states of the atoms must be zero (as it is uncharged), Na has a OS of +1, O is -2 (usually) and Zn is usually +2. From the formula given Na2ZnO2, this is [2 x +1] + [1 x +2] + [2 x-2] =0
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  6. #5  
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    Hi,
    You say that in the hindsight of knowing the formula as you said "From the formula". How can we form the formula without knowing it?
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  7. #6  
    Bullshit Intolerant PhDemon's Avatar
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    You can work out which oxidation states an element is likely to form from it's electronic configuration if you have no other information these can be used to give possible formulae for any combination of elements/ions, with a bit of practice this quickly becomes second nature. In this example sodium has one easily lost valence electron and ALWAYS has a OS of +1, Zn has 2 easily lost electrons and so is found in the +2 state, oxygen has a p4 configuration (2 electrons short of a p6 noble gas configuration) so is most commonly found in the -2 OS, you know you are looking for a neutral molecule so the sum of all the states must equal zero. You then find the stoichiometry that fulfills this requirement using the inferred oxidation states. In this example imagine the formula is NaxZnyOz. From the oxidation states derived from the electronic structures and the condition the molecule is neutral then x +2y- 2z = 0. This can't be solved directly but putting in simple whole numbers rapidly leads to the result x=2, y=1, z=2 giving the formula Na2ZnO2
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