Quantum mechanics (QM ) only gives a partial explanation of the stability of atomic orbitals. QM says that the electrons in an atom exist only in stable, discrete, allowable orbits. But it does not tell us how the electron enters such stable orbit in the first place and how it stays there indefinitely. The stability of the nucleus is also one of the unsolved mysteries in physics. What is the force holding protons together in the nucleus, overcoming the tremendous electrostatic repulsive force between them? The strong nuclear force and the weak nuclear force, two of the supposed four fundamental forces in the universe, have been invented to explain nuclear forces. This paper reveals a new theory on how protons can exist together in the nucleus without invoking any kind of new force. The weak force naturally arises from the new explanation for the strong force.