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by DanielleGuenet
Last updated 12 years ago


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Radioactivity is the spontaneous breakdown of atomic nuclei. It results in the emission of particles or electromagnetic radiation and can be found in both natural and man-made sources.

It was discovered in 1896 by the French scientist Henri Becquerel. While working with uranium, he noticed the photographic plates covered to keep the light out became fogged whenever it was anywhere near the uranium. This suggested some kind of ray had passed through the plates. He discovered radioactivity by accident.

Radioactivity can be found in both naturally and artificially produced sources.The main sources of radiation we are exposed to are Natural Internal Exposure, Natural External Exposure and Medical Exposure. Our body naturally produces some radiation, but we are also exposed to other natural radioactivity such as the sun (cosmic radiation) and the earth (terrestrial radiation).Everyday things such as televisions, microwaves and cell phones all emit small amounts of radiation as well.Some natural radioactive ores include coal (usually contains uranium and thorium), mineral sands (contain a rare mineral monazite), and phosphate (contains uranium and thorium) just to name a few. There are over 60 radioactive elements.



All radioactive nuclides undergo radioactive decay. Also their radiation affects photographic film, ionize surrounding air molecules, make certain compounds fluoresce, and have certain special biological effects.

Radioactive Nuclides

Radiation exposure is the undesirable addition of radioactive material to the body or part of the environment. Different levels of radiation exposure can come from many things such as sunlight, X-rays, consumer products, nuclear weapons, and even your body itself. Radiation exposure can lead to radiation poisoning which causes the deteriotation of organs and can lead to cancer.

Radiation Exposure

The generalization for radioactive elements is that the higher the atomic number, the more radioactive the element is. For example, Uranium which has an atomic number of 92 is much more radioactive than Bismuth which has an atomic number of 83.

Atomic Numbers

The three materials released during radiation are alpha particles, beta particles, and gamma rays.The alpha particle is a relatively heavy and slow particle made up of a helium atom and containing two neutrons and two protons. When alpha particles are emitted, the original nucleus changes - the atomic mass decreases by four and atomic number decreases by two. Alpha particles leave the nucleus at about 16 000 km/s, but due to the fact they are relatively large and slow, they are easily absorbed and a sheet of paper or 5 cm of air is enough to stop them. Alpha particles do not penetrate the outer layer of our skin, but if inhaled or swallowed, living cells will be mutated or killed by the particles.Beta particles are much lighter energy particles. Beta particles are energetic electrons given off by the nucleus of unstable isotopes to restore an energy balance. When beta particles are emitted, the original nucleus changes, the atomic mass stays the same and atomic number increases by one. Beta particles leave the nucleus at about 270 000 km/s. Although beta particles are about 8000 times smaller than alpha particles, they can be stopped by an aluminum sheet a few centimeters thick or by about 10 meters of air. Beta particles damage some of the chemical links between living molecules in the cell. If the damage occurs within generative cells, the damage may be passed to new generations (mutations). Gamma rays are energetic photons or light waves in the same electromagnetic family as light and x-rays. No mass is actually emitted in these rays so the composition of the original nucleus does not change. Gamma rays travel at the speed of light and have the highest penetration power capable of travelling up to 2 km in air and over 30 cm through lead. They are capable of damaging living cells as they slow down by transferring its energy to surrounding cell components.

Alpha, Beta and Gamma

Radiation cannot be detected by human senses, but there are other ways to detect it: radon detectors, Geiger Counters, MicroR meters, neutron REM meters, ionization (ion) chambers or portable multichannel analyzers. The most common method is ionizing radiation. A substance's radioactivity is measured by how many decays per unit of time occur. The standard SI unit for measuring radioactivity is the Becquerel (Bq). 1 Bq = 1 decay/second. Radioactivity can also be measured in the Curie (Ci). 1 Ci = 3.7 x 10^10 decays/sec.


Radiation can be very dangerous to humans because we cannot detect it. This is why radioactive materials and areas must be well-marked.No level of radiation is healthy for you, but depending on the strength of radiation, small amounts of exposure can be virtually harmless.Long term exposure to weak radiation usually lead to long term effects such as to cancers and genetic mutations.Short term exposure to stronger radiation usually lead to shorter term effects such as burns, nausea, weakness, temporary hair loss, and reduced organ whereas long term exposure to strong radiation can lead to long term affects such as premature aging and sometimes even death.


By Danielle and Kristen


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