A substance containing two or more different types of atoms bonded together is called a compound.

Here's why:

* Elements are made up of only one type of atom (like oxygen, gold, or carbon).

* Compounds are formed when two or more different elements chemically combine in a fixed ratio. This bonding creates a new substance with properties distinct from its constituent elements.

For example, water (H₂O) is a compound made of hydrogen and oxygen atoms bonded together. Salt (NaCl) is a compound made of sodium and chlorine atoms bonded together.