A classical model of two oppositely charged particles (the H-atom) is quantized when a relativistic interpretation is used. The H-atom model system shows that the radius is a singular result of the Coulomb potential and space-time curvature in the electric field. This model gives a mechanistic basis for the physics of atoms and demonstrates why atomic orbitals are quantized using a classical particle model. This classical particle model with relativistic interpretation is a mechanistic confirmation of the Quantum nature of atoms. The elegant simplicity of the model combined with the quantisation of the radius and velocity, and zero acceleration of the electron presents a physically consistent model of the atom using particles.