* Atoms are the fundamental building blocks of matter. They are the smallest unit of an element that retains the chemical properties of that element. Think of them as the "letters" of the chemical alphabet.

* Molecules are formed when two or more atoms bond together. They are the smallest unit of a compound that retains the chemical properties of that compound. Think of them as the "words" created by combining the "letters" (atoms).

Here's an analogy:

* Imagine a Lego set. The individual Lego pieces are like atoms. They are the basic building blocks.

* When you combine several Lego pieces together to build a car, that car is like a molecule. It's a structure made up of multiple atoms bonded together.

Key Points:

* Single element molecules: Some molecules consist of just one type of atom. For example, oxygen gas (O₂) is made up of two oxygen atoms bonded together.

* Compound molecules: Other molecules are formed from different types of atoms. For example, water (H₂O) is made up of two hydrogen atoms and one oxygen atom bonded together.

In summary:

* Atoms are the individual building blocks.

* Molecules are formed by combining atoms.