The question "How many carbon atoms does gas have?" is a bit ambiguous. To answer accurately, we need to know what specific gas you're referring to. Here's why:

* Gas is a state of matter: Gas refers to a state of matter where molecules are far apart and move freely. It doesn't specify a particular chemical substance.

* Many gases exist: There are countless gases with different chemical compositions. Some examples include:

* Oxygen (O2): Has no carbon atoms.

* Carbon dioxide (CO2): Has one carbon atom.

* Methane (CH4): Has one carbon atom.

* Propane (C3H8): Has three carbon atoms.

To answer your question, tell me the specific gas you're interested in.