By Barış KARAHASAN α β γ αγβ

RADIOACTIVITY n What is radioactivity and how radioactivity found? n Radioactive particles n Kinds of radioactivity & radioactive decays n How atoms change and what are isotopes? n Radioactivity, dangers and ways of protection n How can we profit by radioactivity?

What is radioactivity and how radioactivity found? n Radioactivity is found in 1896 by Becquerel this discover made a lot of new discoveries in matter’s structural information. This showed all of the nuclei of atoms aren’t stable. Some of them called radioactive, are throwing small particles in form of enterprising rays. After this beam, atoms change their structures. With these results, chemists found that elements are not basic particles, and there were smaller particles called atoms.

Henri Becquerel

Radioactive Substances n Radioactive substances, are substances that release rays or small particles with high speed. Some of these substances found in nature and some of them are produced artificially. Most of natural radioactive elements’ nuclei are heavy. In all elements, great amount of atomic mass are found in nucleus. Because of being too heavy these elements are unstable. This means, these nuclei can not be at rest. They break down by releasing rays. As a result of that they transform into other atoms. This is called RADIOACTIVE DECAY.

Alpha, Beta, Gamma Rays n There are three types of radioactivity. n Gamma n Gamma rays come from the nucleus of the atom of a radioactive isotope. They are the most energetic and most penetrating of all radiation. Some radiation travel as particles not waves and is also emitted by the radioactive isotope. alpha n One is alpha particles that lose energy quickly. A hand or thin piece of paper stops it. n Beta n Beta particles are high speed electrons that travel close to the speed of light and can penetrate a hand but not concrete.

Penetrating powers of rays

Decays

activity curie half life n All radioactive atoms don’t change together Each atom changes in an unexpected moment. Number of radiation per second is called activity of a radioactive substances. Unit of radioactivity is curie. (Name has been taken from Marie Curie; 1 curie= 1000 milicurie). Activity of a radioactive substance lowers by time, because number of atoms decrease because of explosions. Time that pass during decaying of a certain amount of atom is constant. This time is called half life of a radioactive substance. Lets discuss it with an example:

Example: n Half life of Radium is 1622 years. That means 120 grs of radium will left 60 grs after 1622 years. And after another 1622 years past it will remain 30 grs and that will going to continue like that. Note that: This process will continue non-stoply.

n Atoms having the same number of protons but different number of neutrons are called as istopes. Most of the elements have stable and radioactive isotopes. Radioactive isotopes of these kinds of elements can be gained by a nuclear reactor.

Radioactivity, dangers and ways of protection n All radiations in the nature causes breaking down in chemical bonds when pass through substances. When this radiation pass through living cells, it causes mutation. Refining of radioactive substances needs a high level protection. The biological effects depends on the kind of radiation and the organs effected by them. And their half lives and time staying in the organism also effects the mutation. n People use special filtered monitors for preventing the effects of radiation. When working by hands, special gloves and masks are used.For preventing the electromagnetic radiations like gamma and x rays, lead walls and for high energy radiations iron and concrete walls are used. Carbon and water are used against neutrons.

Radiation Effects

How can we profit by radioactivity? n As most of us know, radioactive substances are used in production of atom bomb but these substances are used for benefit on people in many ways like medical, science and industry. For example, gamma rays can pass through human body and have ability of destroying harmful cells. By this effect of gamma rays involuntary cell divisions and some kinds of cancers could be prevented from a point. But these rays can destroy healty cells so operation must realised with great care. Radioactive atoms can be used in labelling substances. For this, some atoms replaced with radioactive atoms. And by the radiation that atom leaves, it is followed. It is used for which substance is going to which part of the body. So medicines’ researches are making by this way. With high energy gamma rays medical equipment in hospitals can be sterilised, which means to disinfect them from microbes.

Radioactive substances used in medical researches

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