As a "chemist", you can easily alter the electron arrangement in the outer energy level of atoms. But you cannot change the nucleus of an atom. Almost any change in the nucleus of an atom will change it from one element to another. This violates one of the basic laws of chemistry - that atoms are neither created nor destroyed in chemical reactions.
The same is not true in nuclear reactions. This type of reaction occurs naturally every day, with the decay of radioactive elements. Even though large amounts of energy of involved, so few atoms actually decay at any one time that there is no immediately observable change. However, over an extended period of time, the energy released can be enough to damage living things.
Nuclear reactions are more physics than chemistry. Because of the large amounts of energy needed to change the atomic nucleus, a device known as a particle accelerator is needed to produce an artificial nuclear reaction.
