While all carbohydrates contain hydrogen and oxygen, they also usually contain carbon atoms. The basic formula for carbohydrates is (CH₂O)n, where n is the number of carbon atoms in the molecule.

Here are some examples:

* Glucose: C₆H₁₂O₆

* Fructose: C₆H₁₂O₆

* Sucrose: C₁₂H₂₂O₁₁

Let me know if you have any other questions!