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Name of the compound CaSi

  1. Oct 21, 2009 #1
    I was asked to give the name of the compound CaSi on a practice exam, which I thought was weird because as far as I knew Ca was always +2 and the periodic table kinda suggests that Si would be -4. So I didn't know how the compound CaSi would exist.

    So I just said Calcium (IV) Silicide and handed it in, even though I was pretty sure Calcium didn't have multiple oxidation numbers.
    And then they said the right answer was Calcium Silicide and I didn't even need the (IV), so now I'm really confused.

    How can CaSi exist, and why don't I need the (IV)?
    Any help will be really appreciated! - I have an exam on Friday.

    Confused again,
    ~Jules~
     
  2. jcsd
  3. Oct 21, 2009 #2
    Re: CaSi

    Ca and Si usually form the compound CaSi2, not CaSi. I'm not sure exactly how CaSi forms, but I suspect it's got something to do with some oxidation states I'm not aware of. You're right, calcium is always +2. As for silicon, it can have a few different oxidation states (I think +2 is one of them), but you were right, -4 is the important one, and the only one you would be expected to know from looking at the periodic table.

    As for the (IV), you don't need to write the charge of a non-transition metal, because they often have only one oxidation state. Two important exceptions are Pb and Sn.
     
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