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Is this the right way of working out bond pairs and lone pairs? Watch

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    (Original post by piece_by_piece)
    Sn has 4 outer electrons
    Cl donates 1 x 2 electrons= 2
    The total number of electrons= 4+2=6
    The number of electron pairs= 6/2=3
    The number of bonding pairs is 2, and there is 1 lone pair.
    The shape is based on trigonal planer.
    Oh so does trigonal planar work for non regular shapes too? This is ridiculous, the sheet i was given is absolute crap.
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    (Original post by DaveJ)
    Hmm well then I wonder why that isn't right... cos Xe only has eight in outer shell.
    Yeah see thats where I thought the spdf thing came in. Ah well, i'm just gonna ignore the 26.
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    (Original post by BrightGirl)
    Yeah see thats where I thought the spdf thing came in. Ah well, i'm just gonna ignore the 26.
    It could be to do with the lanthanides and actinides, confusing things. But that's a guess lol.
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    (Original post by BrightGirl)
    Oh so does trigonal planar work for non regular shapes too? This is ridiculous, the sheet i was given is absolute crap.
    It's based on trigonal planer because there are 3 electron pairs, but I think its actual shape is bent linear. I'm not 100% certain though :ninja: I think the angle would be 117.5 degrees (120-2.5) because the lone pair lone pair repulsions are greater than the bonding pair bonding pair repulsion and this "presses down" on the molecule, causing its bond angle to change.
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    (Original post by BrightGirl)
    Wait hang on a minute.

    For SnCl2, Sn has 4 in its outer shell, and Cl has 7. So there's 1 lone pair and 2 bond pairs, which can't be right cos in my table, we've only done 3 scenarios (3 bond pairs + 1 lone, 2 bond pairs + 2 lone, 4 bond pairs + 2 lone)
    Tin (II) chloride is ionic, not covalent so the issue of shape doesn't arise.
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    SnCl2 would be bent in the gas phase, and is a chloride-bridged solid.
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    Wait surely if there are 2 bonding pairs and 1 lone pair, it isn't trigonal planar, but is instead a bent molecule with bond angle of 110 degrees?
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    (Original post by DaveJ)
    Wait surely if there are 2 bonding pairs and 1 lone pair, it isn't trigonal planar, but is instead a bent molecule with bond angle of 110 degrees?
    Yeah, but its a bent trigonal planar shape with respect to the electron density. As for the exact angles VESPR isn't great for that :p:
 
 
 
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