Atoms form the building blocks of the simplest substances, the chemical elements. Nearly everything on earth is made up of atoms. Each element consists of one basic kind of atom. Tiny as atoms are, they consist of even more minute particles. The three basic types are protons, neutrons, and electrons.
Protons have a positive electrical charge, and electrons have a negative charge.
Neutrons are electrically neutral. The protons and neutrons are crowded into the nucleus, a tiny region at the center of the atom. The nucleus makes up nearly all the mass of an atom. The rest of the atom outside the nucleus is mostly empty space. The electrons whirl through this space.