Atoms can be split up into simpler particle if a particle at very high speed and high energy collides with an atom. Due to this all the energy of the particle is transferred to the atom, and the sub-atomic particles. Now this gained energy, start to moving at high speed, and ultimately divide into two separate atoms.
This principle is used in nuclear fission reaction, where an unstable molecule or atom is made to collide with another high speed particle, so that it splits into smaller, stabler atoms.