The arrangement and number of smaller particles in an atom refer to its atomic structure.

Here's a breakdown of the key components:

* Protons: Positively charged particles located in the nucleus. The number of protons determines the element.

* Neutrons: Neutrally charged particles also located in the nucleus. They contribute to the atom's mass.

* Electrons: Negatively charged particles that orbit the nucleus in specific energy levels called electron shells.

The arrangement of these particles, especially the electrons, determines an atom's chemical properties and how it interacts with other atoms.

Let me know if you'd like more details on any of these components!