A molecule is made up of two or more what?

• A. Ions
• B. Elements
• C. Atoms
• D. Molecules

Answer: (C)

A molecule is formed when two or more atoms are bonded together. That's the defining idea: atoms are the building blocks, and joining them creates the distinct unit we call a molecule. For example, water contains two hydrogen atoms and one oxygen atom bonded together (H2O), while oxygen gas is two oxygen atoms bonded (O2). A molecule can also be made of atoms of different elements, like carbon dioxide (CO2).

An ion is a charged particle, not the basic unit described here, so it isn’t the general answer to what a molecule is made from. An element is a pure substance made of one kind of atom, and while elements can exist as diatomic molecules (like O2), a molecule itself is defined by being two or more atoms bonded, not by being a single element. A molecule isn’t made of other molecules in this basic concept, either.