What is $\left( {S{O_3}} \right)$?

Hint :Sulfur is a non-metal that is plentiful, tasteless, and odorless. Sulfur is a yellow crystalline solid in its natural state. Oxygen is a highly reactive nonmetal and oxidizing agent that forms oxides readily with most elements and other compounds.

Complete Step By Step Answer:
When sulphur dioxide $\left( {S{O_2}} \right)$ reacts with oxygen gas$\left( {{O_2}} \right)$, the result is sulfur trioxide $\left( {S{O_3}} \right)$. This is an exothermic, reversible reaction.
Sulfur trioxide is a poisonous chemical that leads to acid rain by forming sulfuric acid$\left( {{H_2}S{O_4}} \right)$ as it reacts with water $\left( {{H_2}O} \right)$
Sulfuric anhydride and sulfuric oxide are other names for $S{O_3}$. It's used to make sulfuric acid and other chemicals, as well as explosives. Sulfuric acid is a corrosive liquid that is transparent, colorless, and sticky. Sulphine acid, battery acid, and hydrogen sulfate are some of the other names for it.

Additional Information:
The sulfur atom in $S{O_3}$ (Sulfur trioxide) has just three electron regions, making it a Lewis acid. The sulfur atom prefers to accept a pair of electrons. Additionally, $S{O_3}$ is a non-metal oxide that is acidic in nature.

Note :
Sulfur trioxide is a poisonous gas. Death may result from inhaling the vapors, swallowing the substance, or extreme skin contact. Contact with the skin and eyes results in serious burns and blindness.
Sulfur trioxide is a colorless to white crystalline solid that can fume in the sun. When Sulfur trioxide is exposed to the sunlight, it readily absorbs water and emits white fumes. Sulfur trioxide dissolves in and reacts with water to form an aqueous solution of sulfuric acid.