A single silver atom can be considered to be an atomic sized particle of metallic silver. It is the smallest size of silver matter that exists. The diameter of a single silver atom is 0.288 nm. While it is theoretically possible to have a particle of metallic silver that consists of a single atom, in practice particles are much larger and consist of many atoms. Just for reference, a particle one nanometer in diameter would consist of 31 silver atoms, and a 5 nm diameter particle would be about 3900 atoms while a 20 nm diameter particle would contain about 250,000 silver atoms.
Single atoms of metallic silver are drawn to other silver atoms by van der Waals’ force of attraction causing the atoms to form particles made up of many atoms. Because single atoms do not possess a repulsive force, there is nothing to prevent the force of attraction from creating ever larger particles from any available atoms in solution. Larger particles develop an electric double layer of ions surrounding the particle which cause a charge to form called zeta potential. The zeta potential charge of particles in low ionic solutions is negative. The zeta potential creates a repulsive force that causes the particles to to be repelled from each other and uniformly dispersed in the solution. As long as the magnitude of the zeta potential is sufficient to produce a repulsive force that can overcome the force of attraction, the particles remain in suspension.