[OTI]

So, my teacher made this card game called ionic gin where you have to place down ionic compounds. However, all we've learned in class so far is the naming system and not what's "possible". As far as I can see, you can just pile up ions and cancel all the charges. So what are the rules for making ionic compounds? For example, can I have a fluoride, a potassium, and a calcium in an ionic compound?

Thanks.

[potassium_carbonate]

Hi there. Ionic compounds are quite simple once you get the hang of them. An ionic compound can only form between a metal and a nonmetal, or a polyatomic ion. A polyatomic ion is a group of atoms covalently bonded that has a charge. Take, for example, the carbonate ion: [CO₃]^2-.

Metals always form a positive ion (cation) and nonmetals always form a negative ion (anion)

Some examples include:

[K]⁺ [Cl]^-  KCl
[Ca]²⁺ [F]^-  CaF₂

Here is an example with a polyatomic ion. It's also my username.
[K]⁺ [CO₃]²  K₂(CO₃)

I hope this helps! Good Luck!

[OTI]

Thanks! That clears it up a bit. The only problem I have left is with the example I gave. How many different kinds of metals can I have in an ionic bond assuming that there is one non metal?

[potassium_carbonate]

An ion is usually made up of two main "formula units." These can be either an elemental ion, ie, [K]⁺ or a polyatomic ion. (Here is a list of common polyatomic ions--http://yeahchemistry.com/sites/default/files/Common%20Polyatomic%20Ions.PNG)

Combinations include:

A metal and a nonmetal
A cation polyatomic ion and any type of anion
An anion polyatomic ion and any type of cation
A cation polyatomic ion and an anion polyatomic ion.

I hope this was clear.

[OTI]

Yeah. But can I have an ionic compound with a fluoride, a potassium, and a calcium?

[potassium_carbonate]

You can have potassium fluoride or calcium fluoride. I don't believe you can have both.

[OTI]

Okay, thanks. I think I get it now.
Appreciate it.

[potassium_carbonate]

Best of luck!

[Borek]

Yeah. But can I have an ionic compound with a fluoride, a potassium, and a calcium?

I have not heard about this particular compound, but in general - yes, such things happen. They are quite rare, but there are at least three cases worth of remembering:

1. Ammonium iron(II) sulfate AKA Mohr's Salt (NH₄)₂Fe(SO₄)₂·6H₂O (rare case of a stable Fe(II) salt which doesn't get oxidized to Fe(III) when exposed to air).

2. Whole class of alums with a general formula XY(SO₄)₂·12H₂O, where X is a monovalent cation (like Na⁺, K⁺, NH₄⁺) and Y is a trivalent cation (like Al³⁺ or Cr³⁺).

3. Basic and acidic salts - like NaHCO₃ (in which technically H⁺ plays a role of a cation), or basic copper carbonate Cu₂(OH)₂CO₃.

[potassium_carbonate]

Thanks, Borek, I never knew that! 

[missmendeleev]

Depending on whether two or more of the elements form a polyatomic ion together, it is possible.

[Enthalpy]

Minerals are full of examples. "Silicates of X and Y". In Earth's crust, silicates of one metal are rare and sought as useful ore.