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Radioactivity, facts for discoverer of radioactivity

Radioactivity was first discovered by Henri Becquerel in Paris in 1896. He had noticed that some undeveloped photographic plates had been fogged by being left in contact with a bottle of uranium ore. Becquerel concluded after some experiments that the uranium was giving off radiations. Today we know that the atoms of radioactive elements such as uranium and radium are continually disintegrating, and can give off three kinds of radiation. In two of these alpha particles (written a particle) and beta particles (written (3 particles) are given off. An alpha particle consists of a group of two protons and two neutrons, while a beta particle is identical to an electron. Both types of particle come from the atom's nucleus. A third kind of radiation, called gamma rays, does not consist of particles. Gamma rays are like very penetrating X-rays.

uranium-235 - discoverer of radioactivity

The half-life period - discoverer of radioactivity

Facts for discoverer of radioactivity (click to increase)

Atoms of the naturally-occurring radioactive source uranium-235 decay radioactively into atoms of another element by emitting charged particles from their nuclei. But instead of decaying into stable atoms, they decay into atoms which are themselves radioactive. These atoms in turn decay into different atoms and the process continues until a stable atom is reached —in this case atoms of lead-207. A system where atoms decay through a series of elements in this way is called a radioactive series. There are three entirely separate radioactive series found in nature—the uranium-238, the uranium-235 and the thorium-232 series

Facts for discoverer of radioactivity

The half-life period of a radioactive isotope is the time taken for half of the atoms in a sample to decay to atoms of another element. For sodium-24 this is 15 hours. For uranium-238 the half-life period is nearly 5,000,000,000 years

There can be several kinds of the same atom, called isotopes, and many of these are also radioactive. Atoms of carbon, for example, have a number of isotopes which differ only in the number of neutrons contained in their nuclei (plural of nucleus).

Some radioactive isotopes give off only alpha particles. Others give off beta particles. Still others give off both. Today radioactive isotopes can be made artificially for use in industry and medicine. Such isotopes are made by exposing carbon, iodine and other elements found in nature to strong radioactivity in special 'ovens' or reactors using uranium. One more interesting fact for discoverer of radioactivity - scientists working in plants where radioactive sources are being made and used must be protected by special clothing. They also carry small badges or dosimeters containing strips of photographic film. At the end of a day's work the film is developed to see if a dangerous 'dose' of radiation has fogged it.

Radioactivity can be detected by Geiger counters. A small tube contains two metal electrodes connected with an amplifier and a voltmeter, and sometimes a loudspeaker. Radioactive particles passing through the tube cause an electric current to flow, which gives a reading on the voltmeter. The presence of radiation can also be heard as a series of clicks from the loudspeaker.
In medical research scientists can tell what is happening in the brain and other organs of the body using radioactive isotopes. Radioactive iodine, for example, can be injected in very small quantities into the bloodstream. From there the isotope is absorbed by the thyroid glands. By placing a Geiger counter near the throat, the isotope can be detected as it is being absorbed by the thyroid. In this way more can be learned about the thyroid, which influences our rate of growth.

One of the many interesting uses of radioactive isotopes in industry is in the detecting of blocks in oil pipelines. A small plug called a 'go-devil' is put into one end of the pipeline. The flow of oil carries the go-devil to the block, where it stops. In the go-devil a tube of radioactive isotope has been placed. All that has to be done is to move along the length of the pipeline with a Geiger counter, which will start clicking at the exact spot where the go-devil has come to a stop.

As atoms of a radioactive element disintegrate they change or decay to atoms of another element. Atoms of uranium decay eventually to atoms of lead. The time that it takes for half of the atoms to change or decay to atoms of another element is called the half-life period. This ranges from a fraction of a second for some radioactive elements to many millions of years for others. The artificial radioactive isotope sodium-24 has a half-life period of 15 hours. During this time half of the atoms in one gram of sodium-24 would decay to atoms of magnesium, leaving half a gram of the radio-active isotope. During the next 15 hours half of the remaining atoms of sodium-24 would decay, leaving one-quarter of a gram of the radioactive isotope, and so on.

Archaeologists are sometimes able to use the half-life period to measure the age of historic objects made of once-living materials, such as wood. Carbon-14 is a naturally occurring radioactive isotope of carbon found in living things. By measuring the carbon-14 content in an old wooden object and comparing it with the content in a piece of new wood, the age of the wooden object can be calculated.

Radio-carbon dating, as this process is called, was used in studying the Dead Sea Scrolls.  More interesting information about radioactivity and for discoverer of radioactivity you can find on this page, for example 

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