Which element is necessary in the formation of rust?

• A. Nitrogen
• B. Oxygen
• C. Hydrogen
• D. Carbon

Answer: (B)

Verified step by step guidance

1. Understand that rust is a common name for iron oxide, which forms when iron reacts with oxygen and moisture.
2. Recall that rust formation is a chemical reaction involving iron (Fe) and oxygen (O2) from the air, often in the presence of water (H2O).
3. Identify the key element that combines with iron to form rust; this element is oxygen, which reacts with iron to produce iron oxides.
4. Recognize that nitrogen, hydrogen, and carbon are not directly involved in the chemical process that forms rust.
5. Conclude that oxygen is the necessary element in the formation of rust because it chemically bonds with iron to create iron oxide.