Which term describes a pure substance made of only one kind of atom?

• A. Pure substance
• B. Element
• C. Mixture
• D. Solution

Answer: (B)

A substance that is pure and made of only one kind of atom is an element. An element is defined as a pure substance consisting of exactly one type of atom, which can exist as individual atoms or as molecules made of the same atom (like O2 or N2, which are still only oxygen or nitrogen atoms). In contrast, compounds combine two or more different kinds of atoms (like water, which has hydrogen and oxygen), and mixtures or solutions are not pure substances because they contain more than one substance. So the term that fits best is element.