- Oxygen gas is made of only oxygen element
- If a substance is made of one element , then the substance is called an element
- Hence, oxygen gas is an element

- Oxygen gas is an element
- O2 is a chemical formula for oxygen gas
- Therefore, o2 is an element

Therefore, o2 is an element
[Question]Which of these is an element?
[Context]- Oxygen gas is made of only oxygen element 
- If a substance is made of one element , then the substance is called an element 
- O2 is a chemical formula for oxygen gas