Can Calcium and Silicon Form a Compound and How is it Named?

[Jules18]

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~

 

[pzona]

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.

 

[quicknote]

Dear Jules,

I understand your confusion regarding the compound CaSi. Let me explain. The naming of compounds follows a set of rules based on the oxidation states of the elements involved. In this case, both calcium (Ca) and silicon (Si) can have multiple oxidation states.

Calcium typically has a +2 oxidation state, but it can also have a +4 oxidation state in certain compounds, such as CaF2. Similarly, silicon usually has a -4 oxidation state, but it can also have a +4 oxidation state in compounds like SiO2.

In the case of CaSi, the oxidation states of each element are balanced to form a neutral compound. Calcium has a +2 oxidation state and silicon has a -4 oxidation state, resulting in a net charge of 0 for the compound. Therefore, the correct name for this compound is simply Calcium Silicide, as you were told. The use of (IV) is not necessary because it is implied by the overall charge of the compound.

It is important to keep in mind that the oxidation states of elements can vary in different compounds, and this is why it is important to use the correct naming conventions. I hope this clears up your confusion and helps you on your upcoming exam.

Best of luck,