In this paper it has been studied how does forces act between stable atomic particles. To do the findings it has been postulated that a tiny particle type is running throughout the space with some constant velocity. The particle of that type is so tiny that those particles almost don’t collide with each other and hence at any point in space if a solid atomic particle is being kept then the pressure on that atomic particle from all angles are same. However, if a second atomic particle is being brought closer to that former atomic particle, then shadows form on both atomic particles by each other atomic particles. Hence, pressure difference happens, and attraction force is being perceived. Also, it has been postulated that all atomic particles are made of this tiny particle type. As atomic particle spins it scatters those tiny particle and repulsive force is being perceived. In this paper this postulate has been verified mathematically and finally arrived at a formula of net force acting between two stable atomic particles. This mathematical model is successfully predicting change pattern of atomic radius with change in atomic numbers. Also, it is conforming that velocity of light is constant. This same model matches the Lennard-Jones potential function pattern between two atoms.