10-11 meters

More at 10 picometers

One of the most successful scientific theories is the theory of the atom. Predictions of the energy levels of electrons orbiting the nucleus agree with experimentally derived values. Neils Bohr was the first to provide a workable atomic theory. With refinements and adjustments provided by deBrolie, Heisenberg, Pauli, and others, the physical basis of chemistry is very well understood. Atomic theory explains the electromagnetic spectrum of elements, and atomic and molecular bonding.