Question

Which list only includes terms that describe oxygen gas, O2?
• atom, compound, molecule
• atom, element, molecule
• compound, molecule, pure substance
• element, molecule, pure substance

Answer 1

The correct list that only includes terms that describe oxygen gas (O2) is:

• element, molecule, pure substance

O2 is an element because it is made of only oxygen atoms, it is a molecule because it consists of two oxygen atoms bonded together, and it is a pure substance as it has a uniform composition.