Atoms are the smallest part of matter that cannot be broken down. Atoms are so small that even with the most powerful microscope you could not see them. The number of protons in the nucleus of the atom determines which type of atom it is. The three parts of the atom are the Proton, Neutron, and Electron.
The earliest written idea of what an atom was, came from the Greeks around 400 B.C. They believed that atoms were very small particles but the Greeks could not describe them.
The nucleus of an atom is the protons and neutrons combined together. A valence electron is an electron that is farthest from the nucleus.
The protons are positively charged particles, neutrons are neutral, and electrons are negatively charged