The three components that make up an atom are protons, electrons and neutrons. Protons possess a positive electrical charge, electrons are negatively charged and neutrons have no electrical charge at all.
The most numerous of these particles, electrons, also comprise the smallest part of the atom. The largest part of the atom is made up of a nucleus compromised of protons and neutrons, which occur in equal numbers for all atoms, excluding hydrogen. The electrons of an atom are not attached to the nucleus. They instead move around it in a manner similar to the way planets orbit the sun.