Pure substances are defined as substances that are made of only one type of atom or only one type of molecule (a group of atoms bonded together). There are two types of Pure Substances an Element and a Compound.
Element is a part or aspect of something abstract, especially one that is essential or characteristic. It is also made of only one type of atom.
Iron is an element because it is made up of one atom.
Compounds are things that are composed of two or more separate elements; a mixture.
Mixture is a substance made by mixing other substances together. There are two different types of mixture Heterogeneous and homogeneous.