Artificially Induced Radioactivity
In a nutshell, radioactivity is described as the interaction with matter by heavier elements to produce ions. Although radioactivity is observed as a natural occuring process, it is a process that can also be artificially induced. Radioactivity is artificially induced through the bombarding atoms of a specific element by radiating particles, thus creating new atoms existing from another type of element.
Ernest Rutherford was a prominent New Zealand scientist, and a winner of the Nobel Prize in chemistry in 1908. Amongst his vast list of discoveries, Rutherford was also the first to discover artificially induced radioactivity. Through the bombardment of alpha particles against the nuclei of 14N (7 protons/electrons) Rutherford produced 17O (8 protons/electrons) and protons. Through this observation, Rutherford concluded that atoms of one specific element can be made into atoms of another element through the this discovered process of artificially induced radioactivity
Rutherford was the first intellectual to create protons outside of the atomic nuclei, and 17O which was a nonradioactive isotope of oxygen.
Irene Joliet-Curie and Frederic Joliot
Irene Joliet-Curie and her husband Frédéric both were French scientists who shared winning the Nobel Prize award in chemistry in 1935 for artificially synthesizing a radioactive isotope of phosphorus by bombarding aluminum with alpha particles. 30P (15 protons/elections) was the first radioactive nuclide obtained through this method of artificially inducing radioactivity.
Artificially Induced Radioactivity Today
Before this discovery of artificial induction of radioactivity, it was a common belief that atoms of matter are unchangeble and indivisible. After the very first discoveries made by Ernest Rutherford, Irene Joliot-Curie and her husband, Frederic Joliot, a new point of view was developed. The point of view that although atoms appear to be stable, they can be transformed into new atoms with different chemical properties. Today over one thousand artificially created radioactive nuclides exist, which considerably outnumber the nonradioactive ones created.
Activation by neutron capture
Activation (or radioactivation) involves making a radioactive isotope by neutron capture, e.g. the addition of a neutron to a nuclide resulting in an increase in isotope number by 1 while retaining the same atomic number. Activation is often an inadvertant process occuring inside or near a nuclear reactor, where there are many neutrons flying around. For example, Cobalt-59 has a large neutron capture cross-section, making it likely that Co-59 in or near a nuclear reactor will capture a neutron forming the radioactive isotope Co-60. To avoid this inadvertant activation, the use of cobalt in or near reactors is minimized to the extent it is practical. Light water coolant in nuclear reactors inevitably contain traces of impurities which inadvertantly become neutron-activated making the primary water coolant radioactive. In boiling water reactors (BWR), the radioactive water/steam contaminates the inside of the steam turbine with radioactivity. Maintenance in a BWR steam turbine requires radiological controls to avoid contamination of the maintenance personnel.
Related Example Problems
Solution: A unknown particle is produced with 56Mn, in order to find the mass number (A) of the unknown we must subtract the mass number of the Manganese atom from the mass number of the Cobalt atom plus the neutron being thrown. In simpler terms,
Now, by referring to a periodic table to find the atomic numbers of Mn and Co, and then subtracting the atomic number of Mn from Co, we will recieve the atomic number of the unknown particle
Thus, the unknown particle has A = 4, and Z = 2, which would make it a Helium particle, and the nuclear formula would be as follows:
2. Write a nuclear equation for the production of 147Eu by bombardment of 139La with 12Ca.
Solution: Like the above example, you must first find the mass number of the unknown particle.
Thus,the mass number of the unknown particle is 4. Again by referring to a periodic table and finding the atomic numbers of Lanthanum, Carbon and Europian, we are able to calculate the atomic number of the unknown particle,
The atomic number for the unknown particle equals to zero, therefore 4 neutrons are emitted, and the nuclear equation is written as follows: