* Elements are made of atoms: Sodium (Na) is an element, and elements are made up of only one type of atom.

* Atoms are the smallest unit: Atoms are the smallest particles that still retain the properties of an element. You can't break down a sodium atom into something smaller and still have sodium.

So, the answer is: A single sodium atom is all that is needed to make up the element sodium.

However, you might be thinking about a sample of sodium metal. In that case, you would have a huge number of sodium atoms all joined together.