What happens when sulphur reacts with oxygen? 

SO₂ is formed 

The correct answer is option 1. SO₂ is formed.

The reaction between sulfur (S) and oxygen (O₂) involves the process of combustion, resulting in the formation of sulfur dioxide (SO₂). The balanced chemical equation for this reaction is:

\[ \text{S} + \text{O}_2 \rightarrow \text{SO}_2 \]

Here is an explanation of the reaction:

1. Combustion Reaction:  Sulfur undergoes combustion when it reacts with oxygen. Combustion is a chemical process that involves the rapid combination of a substance with oxygen, usually accompanied by the release of heat and light.

2. Formation of Sulfur Dioxide (SO₂): In this specific reaction, sulfur combines with oxygen molecules to form sulfur dioxide. The chemical formula for sulfur dioxide is \( \text{SO}_2 \).

\[ \text{S} + \text{O}_2 \rightarrow \text{SO}_2 \]

3. Oxidation State: In the process, sulfur undergoes oxidation, meaning it gains oxygen atoms. The oxidation state of sulfur changes from 0 in elemental sulfur to +4 in sulfur dioxide.

4. Physical Properties: Sulfur dioxide is a colorless gas with a pungent odor. It is soluble in water, forming sulfurous acid (\(\text{H}_2\text{SO}_3\)). Sulfur dioxide is also an important component in atmospheric chemistry and is involved in various environmental processes.

This reaction is a fundamental example of how nonmetals, such as sulfur, can undergo combustion reactions with oxygen to form oxides. The specific oxide formed depends on the conditions of the reaction and the stoichiometry of the elements involved.