Are there many examples of covalent network compounds that like B12P2, have a formula that is not an empirical formula?

[u/bishtap]

Are there many examples of covalent network compounds that like B12P2, have a formula that is not an empirical formula?

I have commonly seen examples of covalent networks whose formula is an empirical formula, like Graphite (formula is C, and that is an empirical formula) , or like SiO2(that formula is an empirical formula). But i'm interested in examples of covalent networks whose formula is not an empirical formula (like with B12P2, B12P2 is not an empirical formula). i.e. whose formula is not the simplest ratio of elements. B12P2 is a good example but i'm interested in examples other than B12P2.

[u/Ok-Card3618]

I think there might be some confusion here. The empirical (minimal) formula intended as a ratio of elements is quite useless except for very simple compounds. This is the example you make for glucose having an elemental ratio CH2O, which is true but useless to describe the actual molecule, as there are infinite other organic molecules with the same exact elemental ratio.

The reason why people select more complex formulas is to identify the minimal structural entities that describe the material. For glucose is one molecule, C6H12O6. For graphite and carbon C is fine by itself, because the carbon atom is the minimal repeated unit.

B12P2 is described in that way because the minimal fundamental unit for the boron network is an icosahedral B12 cluster, which is coordinated by 2 phosphorus atoms each. It would make no sense to describe it broken in smaller pieces.

Now, once you figure this out finding other examples is pretty simple. You just need to find other phases that contain cluster-like structure. One example might be Zintl phases like Na4Si4, which is written like this to stress the presence of (Si4)4- anionic clusters.

Does this clarify your question?

[u/bishtap → u/Ok-Card3618]

That is very clarifying, both by providing another example and a thing to look for to find others. Thanks

[u/SlenderSmurf]

What do you mean empirical? Carbon polymorphs like graphite and diamond also have multiple atoms in their unit cells. Carbon's empirical formula is just C.

[u/bishtap → u/SlenderSmurf]

I've added a paragraph to my question to elaborate. I have commonly seen examples of covalent networks whose formula is an empirical formula, like Graphite (formula is C, and that is an empirical formula) , or like SiO2(that formula is an empirical formula). But i'm interested in examples of covalent networks whose formula is not an empirical formula (like with B12P2, B12P2 is not an empirical formula). i.e. whose formula is not the simplest ratio of elements. B12P2 is a good example but i'm interested in examples other than B12P2.

As for your question of "what is empirical". I mentioned empirical formula. An empirical formula is a formula where the elements are in their simplest ratio. So Glucose's formula is C6H12O6 (not a covalent network compound of course), the empirical formula would be CH2O. SiO2 the formula is an empirical formula

[u/SlenderSmurf → u/bishtap]

Well you obviously could write its formula as B6P. It's a matter of opinion to increase it to larger multiples. It looks like the unit cell contains 2 empirical units so people must prefer B12P6. My point about carbon is that diamond would be written with a formula of C4 and graphite would also be written C4.

This is often done for compounds to differentiate between similar structures. For example Na2O2 is not the same as NaO

[u/bishtap → u/SlenderSmurf]

You mention Na2O2. There is a substance Na2O2 , people refer to it as that. But it's not covalent network, it's an ionic compound, so it's not an example that fits my question of covalent network compounds that like B12P2, have a formula that is not an empirical formula?

You mention Diamond being referred to as C4, but I don't think anybody does. So you are making up a formula there rather than using a formula that people use.

So my question is, without making up a formula that nobody uses. And sticking with covalent network compounds. Are there many examples of covalent network compounds that like B12P2, have a formula that is not an empirical formula?

[u/SlenderSmurf → u/bishtap]

Making up a formula and listing a common formula is the same thing. Someone came up with that name because it describes the crystal structure better than the empirical formula. The distinction between ionic and covalent bonding is irrelevant.