Here's a breakdown:

* Atoms: The fundamental building blocks of all matter. They are incredibly small and consist of even smaller particles:

* Protons: Positively charged particles found in the nucleus of an atom.

* Neutrons: Neutrally charged particles also found in the nucleus.

* Electrons: Negatively charged particles that orbit the nucleus in shells.

* Elements: Each unique type of atom is called an element. There are over 100 known elements, each with a different number of protons in its nucleus. Examples include hydrogen, oxygen, carbon, and gold.

* Molecules: Two or more atoms bonded together form a molecule. Water (H₂O) is a molecule made of two hydrogen atoms and one oxygen atom.

* Compounds: When two or more different elements combine chemically, they form a compound. Water is a compound because it is made from two different elements: hydrogen and oxygen.

Here's a simplified analogy:

Think of building blocks. Atoms are like the individual blocks. You can combine different blocks to create more complex structures. Similarly, you can combine atoms to create molecules and compounds.

Key takeaway: The smallest unit of matter that retains the properties of an element is an atom.