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Thread: Valency

  1. #1 Valency 
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    Can anyone explain to me the rules the govern the valency of elements please?

    I would like to understand this because of it`s relevancy in biology. I know the valency of the more common elements, hydrogen, carbon, oxygen, nitrogen and some others, can anyone tell me the layout for stable outer shells, it`s been a while since i studied chemistry.


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  3. #2  
    Universal Mind John Galt's Avatar
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    While we are waiting for someone to come up with a short simple explanation, have you tried googling for a response?

    In the meantime Wikipedia, as is often the case, has a reasonable treatment.
    http://en.wikipedia.org/wiki/Valency_%28chemistry%29


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  4. #3  
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    Quote Originally Posted by Ophiolite
    While we are waiting for someone to come up with a short simple explanation, have you tried googling for a response?

    In the meantime Wikipedia, as is often the case, has a reasonable treatment.
    http://en.wikipedia.org/wiki/Valency_%28chemistry%29
    I did try google in the past, it wasn`t very helpful. How many electrons does an element have to have in each shell for it to be stable?
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  5. #4  
    Forum Senior silkworm's Avatar
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    Do you know the 1s, 2s, 2p, etc. sublevels?

    The valence electrons are considered the electrons in the unfilled top level. And this goes by group number (outside of the transition metals).

    Hydrogen is group 1, so it has 1, as is Li, Na, K, Rb, Cs, and Fr.

    Be, Mg, Ca, Sr, Ba, Ra all have 2, they're group 2.

    B, Al, Ga, In, Tl, all have 3, and so on.

    The noble gases all have 8, which leads to their stability in the Lewis sense because it has a happy octet. Although it actuality it's a bit more complicated then that. But the Noble gases are considered the most stable elemets because of this happy octet in their valence shell.

    Determining the valency of the transition metals is a bit more complex, and other than there being many trace elements necessary for biological functions that are transition metals, you're primarily going to be dealing with row 2 elements of groups 1-8 and so, Hydrogen in row 1, and Na, P, S, and Cl in row 2.

    I hope that makes sense, and if you need clarification please ask. I'm a chemist.
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  6. #5  
    Forum Senior silkworm's Avatar
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    Quote Originally Posted by Question
    Quote Originally Posted by Ophiolite
    While we are waiting for someone to come up with a short simple explanation, have you tried googling for a response?

    In the meantime Wikipedia, as is often the case, has a reasonable treatment.
    http://en.wikipedia.org/wiki/Valency_%28chemistry%29
    I did try google in the past, it wasn`t very helpful. How many electrons does an element have to have in each shell for it to be stable?
    The 1st level, with that are H and He's valence shells have 2.

    The 2nd level, which is the 2nd row, has 8. Meaning that they full valence shell of Neon has 8 electrons, but it has 10 total.

    At level 3, the level is also 8, BUT things get complicated here when you go to the fourth row. But for biology you wouldn't have to concern yourself with this anyway.
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