Carbon dioxide

Carbon dioxide (chemical formula CO₂) is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom.

1. CO₂ is a trace gas comprising 0.039% of the atmosphere. 
2. Two oxygen atoms covalently bonded to a single carbon atom.
3. Carbon dioxide is used by plants during photosynthesis to make sugars.
4. Carbon dioxide has no liquid state at pressures below 5.1 atmospheres. At 1 atmosphere (near mean sea level pressure), the gas deposits directly to a solid at temperatures below −78 °C (−108.4 °F; 195.1 K) and the solid sublimes directly to a gas above −78 °C. In its solid state, carbon dioxide is commonly called dry ice.
5. CO₂ is an acidic oxide: an aqueous solution turns litmus from blue to pink. It is the anhydride of carbonic acid, an acid which is unstable in aqueous solution.