Final answer:
The symbol 'O' represents an individual atom of oxygen, while the formula 'O₂' represents a molecule of oxygen, which consists of two oxygen atoms bonded together. This distinction is due to chemical convention and to clearly distinguish between single atoms and molecules.
The correct answer is: d) Both a and c
Step-by-step explanation:
a) Chemical convention: The symbols used for elements represent individual atoms, while chemical formulas represent the composition of molecules. The chemical convention distinguishes between the symbol for an individual atom of an element (e.g., "O" for oxygen) and the formula for a molecule, which may consist of multiple atoms of the same or different elements (e.g., "O₂" for a molecule of oxygen).
c) To distinguish between atoms and molecules: Symbols for elements represent single atoms, whereas chemical formulas represent the arrangement and composition of atoms in molecules. The differentiation helps convey whether the expression refers to an individual atom or a group of atoms bonded together in a molecule.
So, the correct answer is "Both a and c."