A pure substance that contains more than one type of atom is called a compound.

Here's why:

* Pure substance: Means it's made up of only one type of molecule or one type of atom.

* More than one type of atom: This means the molecule is formed by combining different elements.

For example:

* Water (H₂O) is a compound because it's made of hydrogen (H) and oxygen (O) atoms.

* Sodium chloride (NaCl) is a compound because it's made of sodium (Na) and chlorine (Cl) atoms.

Let me know if you'd like more examples!