Electrical forces that act on positively charged nuclei of various atoms and negatively charged electronic clouds that extend around these nuclei rule chemistry. The three other fundamental forces in physics, namely strong and weak interactions that act on the protons and neutrons of the nuclei and gravity, do not play any role in chemistry.
The first two are much stronger than electromagnetic forces and consequently correspond to much larger energy level separations than energies due to electromagnetic interactions. It impliesthat in chemistry all nuclear levels are ground state levels or, in other words, nuclei are always in their fundamental state. The third fundamental force, gravity, is orders of magnitude too weak to have any detectable influence on electromagnetic levels.
The elementary constituents in chemistry are therefore atoms, made of positively charged nuclei that are always in their ground nuclear state and surrounded by negatively charged electronic clouds. The precise knowledge of the structures of these electronic clouds is the object of chemistry. Atoms are the simplest arrangement of all these electrons and nuclei.
They are not the most stable ones. Two H-atoms, for instance, the simplest atoms made of single protons surrounded by single electrons, are attracted to each other in such a way that their initially separated electronic clouds mix together so as to form a single cloud occupied by both electrons with different spins, which keep the two protons separated by a well-defined distance.