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'Dot and cross' diagram of Ca(OH)2

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    Hey,

    I've been doing some past papers for chemistry and this was one of the questions, the mark scheme doesn't offer a picture so naturally I don't know if I'm correct or not. Could someone willing please draw it out for me? Thanks very much.
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    I'll show you mine if you show me yours. :ninja:


    ...in other words, why don't you show us what you've drawn and we'll tell you if you're correct. Instead of us giving you the answers straight up.
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    (Correct me if its wrong please)

    Is it something like this:

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    (Original post by Akkuz)
    (Correct me if its wrong please)
    Erm, Ca(OH)2 is ionic
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    Calcium's a metal so there'd be an Ionic bond ... :ninja:

    EDIT: Aw crap, EierVonSatan beat me to it.
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    (Original post by EierVonSatan)
    Erm, Ca(OH)2 is ionic
    This.

    You do two square bracets.

    Like this
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    (Original post by PeanutButterJellyTime)
    Like this
    There is a covalent bond between the O and H, though.
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    (Original post by EierVonSatan)
    There is a covalent bond between the O and H, though.
    Its only A levels. :>.<: they don't care.
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    (Original post by PeanutButterJellyTime)
    Its only A levels. :>.<: they don't care.
    lol I bet they would :p:

    Here is what it should look like.
    Attached Images
  1. File Type: pdf Ca(OH)2.pdf (49.7 KB, 4673 views)
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    (Original post by EierVonSatan)
    lol I bet they would :p:

    Here is what it should look like.
    Edexcel isn't really picky. Other examining boards such as AQA and OCR can be at times.

    BTW nice use of Colour
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    I'm on OCR ^^

    I'm not sure where your blue electron came from, I drew this, I think it's the same?

    EDIT: Apologies for the very scruffy writing.

    EDIT2: After looking at it again, my OH bonds wouldn't have a negative charge...I think I understand now. The electron from Ca pairs with the oxygen and the other electron of oxygen bonds with hydrogen. But that wouldn't have a negative charge? Arghh, confused.
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    (Original post by Woody.)
    I'm on OCR ^^

    I'm not sure where your blue electron came from, I drew this, I think it's the same?

    EDIT: Apologies for the very scruffy writing.

    EDIT2: After looking at it again, my OH bonds wouldn't have a negative charge...I think I understand now. The electron from Ca pairs with the oxygen and the other electron of oxygen bonds with hydrogen. But that wouldn't have a negative charge? Arghh, confused.
    I think its because there are 3 different types of atom's (Ca, H and O), hence, you must indicate that they have distinct electrons.

    Correct me if i'm wrong EierVonSatan
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    Yeah, thanks. I do understand the blue part now, but I'm rather confused on the edited areas
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    (Original post by PeanutButterJellyTime)
    Edexcel isn't really picky. Other examining boards such as AQA and OCR can be at times.

    BTW nice use of Colour
    Thanks

    I would be that picky :p:

    (Original post by Woody)
    Yeah, thanks. I do understand the blue part now, but I'm rather confused on the edited areas
    Okay in ionic compounds metals donate electrons to non-metals, so the outer two electrons of calcium have been donated to the OH's, hence they have 1 blue electron and a negative charge each. This leaves Ca with a 2+ charge and a full outer shell.

    Oxygen has six electrons (red) + 1 from Ca (blue) and is sharing one of it's electrons with the hydrogens (green). Hope that helps
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    (Original post by EierVonSatan)
    Erm, Ca(OH)2 is ionic
    ohh yeah, haha. cheers. :banghead:
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    (Original post by EierVonSatan)
    lol I bet they would :p:

    Here is what it should look like.

    yeh but they ask you to draw a 'dot and cross diagram' not a ' 3 different colour dots diagram', so what would be the best way to answer this question?
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    (Original post by EierVonSatan)

    Oxygen has six electrons (red) + 1 from Ca (blue) and is sharing one of it's electrons with the hydrogens (green). Hope that helps

    so basssiicaaally

    Ca(OH)2 has a mixture of ionic and covalent bonding

    covalent bonding between the Oxygen and Hydrogen, and ionic between Ca and O( causing the OH ion to have a negative charge)

    am i right or am i right?
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    (Original post by sonic23)
    so basssiicaaally

    Ca(OH)2 has a mixture of ionic and covalent bonding

    covalent bonding between the Oxygen and Hydrogen, and ionic between Ca and O( causing the OH ion to have a negative charge)

    am i right or am i right?
    You're right...
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    Yeah, I think I do get it now, cheers

    Could you verify that my drawing of it is correct? Thanks.
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    (Original post by Woody.)
    Yeah, I think I do get it now, cheers

    Could you verify that my drawing of it is correct? Thanks.
    You need to show that the extra electron on the oxygen doesn't originate from the oxygen somehow, otherwise it's fine
Updated: December 23, 2008
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