Two types of pure substances are:
Elements: These are substances that cannot be broken down into simpler substances by chemical means. Each element is made up of only one type of atom. Examples of elements include oxygen, carbon, and gold.
Compounds: These are substances that are made up of two or more elements that are chemically combined in fixed proportions. Compounds can be broken down into their constituent elements by chemical means. Examples of compounds include water (made up of hydrogen and oxygen) and sodium chloride (table salt, made up of sodium and chlorine).