The chemical formula for carbon nitride depends on the specific compound you're interested in. There are several possible forms, with varying ratios of carbon and nitrogen atoms. Here are a few examples:

* C3N4: This is the most common and well-studied form of carbon nitride. It's a polymer with a layered structure, similar to graphite.

* C2N2: This is a small, linear molecule known as cyanogen. It's a highly toxic gas.

* CN: This is a radical species, also known as cyano radical. It's highly reactive and short-lived.

So, you'll need to provide more context about the specific carbon nitride you're interested in to get the accurate chemical formula.