Check whether the substance is made of only one type of atom
If it contains only one type of atom, identify it as an element
If it contains two or more different types of atoms chemically bonded, identify it as a compound
Look at the chemical formula
A formula with one element symbol only indicates an element
A formula with more than one different element symbol indicates a compound
Determine whether the substance can be broken down by chemical means
If it cannot be broken down into simpler substances, it is an element
If it can be chemically broken down into simpler substances, it is a compound
Compare its properties with known elemental or compound behavior
Use periodic table information to verify element identity
Use naming rules to verify compound identity
Check for a fixed ratio of different atoms
A fixed ratio of different atoms indicates a compound
Confirm with laboratory analysis if needed