Lucy Boanas, of Ilam School, asks :-

Sophie Goodwin, of Mokoia Intermediate School, asked:-

How do you split an atom?

John Campbell, a physicist and a biographer of Ernest Rutherford, responded.

Our countryman, Ernest Rutherford, received the 1908 Nobel Prize in Chemistry for explaining that naturally occuring radioactivity was due to very heavy atoms, such as uranium, spontaneously splitting into lighter atoms and ejecting a small particle at very high speeds. He named the two main types of particles as alpha and beta, the first two letters of the greek alphabet. The alpha particle is the core of the helium atom.

In 1917 he became the first person in the world to split an atom, by firing high speed alpha particles, ejected from radioactive polonium atoms, into nitrogen gas. Occasionally one of the alpha particles penetrated into the core of the nitrogen atom and made it unstable so it split into an oxygen atom and the light core of a hydrogen atom which was then ejected at high speed. So, firing the appropriate high speed sub-atomic particle at an appropriate atom is one way to split an atom.

Because the alpha particle and the core of other atoms have the same type of electrical charge on them they repel each other, just as the long hairs on your head do when electrically charged while being combed with a plastic comb on a dry day, and seldom collide so this is a very inefficient process. In 1935 an Italian, Enrico Fermi, fired an uncharged sub-atomic particle, the neutron, at atoms. The neutron was not repelled so it could easily enter the core of an atom thus making many unstable. These then split into a lighter atom plus ejected particles. Several of these artificially produced radioactive elements are used by doctors to examine parts of the body which may not be working correctly.