READ: Radiation

READ: Radiation

You may have seen this sign before—maybe in a hospital. The sign means that radioactive materials are present and special safety precautions need to be taken. These materials are used for diagnosis and treatment of many diseases. The people using these materials are specially trained to handle them safely. Radioactive materials can be dangerous and should be respected, but need not be feared.

The world's first nuclear power plants began operations in the 1950s in both the United States and what was then the Soviet Union. There are now over 400 nuclear power plants operating throughout the world. Nuclear power uses the energy released from a process called nuclear fission to turn water into steam, which turns a turbine and generates electricity. Nuclear fission is also responsible for the destructive power of the atomic bomb. Nuclear power has been very controversial throughout its history due to the risk of radiation release in the case of an accident and the problems of dealing with the radioactive waste generated by the plant. In this module, you will learn about nuclear chemistry. Nuclear reactions involve changes to the nuclei of atoms, whereas ordinary chemical reactions only involve rearrangements of electrons and atoms.

For instance, the man in this old illustration below was an alchemist.  Alchemists, who lived during the Middle Ages, were people who strived to turn lead into gold. They tried all sorts of chemical reactions involving lead, but they were never able to produce gold. Today, scientists know that one element cannot be changed into another by chemical processes. However, there is a way that some elements can change into others.  For an atom of one element to change into a different element, the number of protons in its nucleus must change. That's because each element has a unique number of protons. For example, lead atoms always have 82 protons, and gold atoms always have 79 protons.  In order to understand nuclear chemistry, there is specific terminology you must know.

Radioactivity

Radioactivity is the ability of an atom to emit, or give off, charged particles and energy from its nucleus. The charged particles and energy are called by the general term radiation. To distinguish the difference between radioactivity and radiation, think about radioACTIVITY as an action. This is what the unstable nuclei does in order to become stable (emits particles and energy). What is being emitted from the nucleus is the radiation.  

Only unstable nuclei emit radiation. They are unstable because they have too much energy, too many protons, or an unstable ratio of protons to neutrons. For example, all elements with more than 83 protons—such as uranium, radium, and polonium—have unstable nuclei. They are called radioactive elements. The nuclei of these elements must lose protons to become more stable. When they do, they become different elements.

Radioactivity was actually discovered by accident. In 1896, Henri Becquerel was studying the effect of certain uranium salts on photographic film plates. He believed that the salts had an effect on the film only when they had been exposed to sunlight. He accidentally found that uranium salts that had not been exposed to sunlight still had an effect on the photographic plates.  Pierre and Marie Curie, associates of Becquerel at the time, showed that the uranium was emitting a type of ray that interacted with the film. Marie Curie called this radioactivity. Marie Curie went on to discover the radioactive elements polonium and radium. She won two Nobel Prizes for her discoveries and work with radiation.

Georgia Virtual, Nuclear Chemistry, CC BY-NC-SA 3.0

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