If a chemical appears on the periodic table, it is an element.
An element is a pure substance that is made up of similar atoms.
It is the simplest particle of a substance that can not be broken down into simpler units using chemical means. Examples of elements include sodium metal, oxygen gas, magnesium metal, silicon, etc.
A compound, on the other hand, is a substance made up of two or more atoms that are different.
A compound results from the chemical combination of more than two elements, for example, H2O, NaNO3, etc.
