The neutron was discovered in 1932. It was already know that atoms could be split into smaller, lighter atoms, using deuterium (heavy hydrogen) nuclei and %alpha particles (helium nuclei). Both these particles are positively charged so can be accelerated by electric fields to the high speeds needed to disintegrated atomic nuclei. They are however, positively charged, so are repelled by the positively charged nuclei they must approach in order to disintegrate. Very few of these particles were able to approach the target nuclei sufficiently close.
Now the neutron gave physicists a very important method of splitting the atom. The neutron, being electrically neutral, did not feel the force of repulsion as it approached the nucleus. As investigation proceeded throughout the 1930's, it was found that the majority of nuclei could be disintegrated by bombardment with neutrons and a range of disintegration products were obtained. Subsequrent decays are also possible if any of the products of the disintegration are unstable. A good example is the bombardment of lithium.
The decay of the tritium nucleus
is given by
Sometimes the end product is the same as the original bombarded nuclei, as when magnesium is bombarded. On capturing a neutron a
nucleus becomes
nucleus with the ejection of a proton. The sodium (Na) nucleus is radioactive with a half life of about 15 hours. It decays back into magnesium with the ejection of a
- particle. The reactions are shown below.
The sodium 24 is useful in studies of blood circulation.