There isn't a gas that "gives off oxygen" in the sense of naturally producing it.

Here's why:

* Oxygen is an element: Oxygen is a fundamental building block of matter, not something that can be produced by a chemical reaction.

* Photosynthesis is the source of oxygen: The primary way oxygen is released into the atmosphere is through photosynthesis by plants, algae, and some bacteria. They use sunlight, carbon dioxide, and water to create energy and release oxygen as a byproduct.

However, you can get oxygen from certain chemical compounds:

* Decomposition of oxygen-containing compounds: Some compounds, like hydrogen peroxide (H₂O₂), can decompose to release oxygen gas.

* Electrolysis of water: Passing an electric current through water (H₂O) will split it into hydrogen (H₂) and oxygen (O₂) gas.

Let me know if you have any other questions!