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Releasing Particles
Radioactivity occurs when an atomic nucleus breaks down into smaller particles. There are three types of particles: alpha, beta, and gamma. Alpha particles are positively charged, beta particles are negatively charged, and gamma particles have no charge. The particles also have increasing levels of energy, first Alpha, then Beta, and finally Gamma, which is the fastest and most energetic of all the emission particles.
Half of a Life
The term half-life describes the time it takes for the amount of radioactivity to go down by one half. Let's say you have some uranium (don't try this at home) and it's radioactive. When your measurements tell you that the level of radioactivity has gone down by one-half, the amount of time is the half-life. Every element has its own unique half-life. The half-life of uranium-235 is 713,000,000 years. The half-life of uranium-238 is 4,500,000,000 years. That is a long time to wait for the radioactivity to decrease.
There is even a radioactive isotope of carbon, carbon-14. Normal carbon is carbon-12. C-14 has two extra neutrons and a half-life of 5730 years. Scientists use C-14 in a process called carbon dating. This process is not when two carbon atoms go out to the mall one night. Carbon dating is when scientists try to measure the age of very old substances. There are very small amounts of C-14 in the atmosphere. Every living thing has some C-14 in it. Scientists measure the amount of C-14 in the things they dig up to estimate how old they are. They rely on the half-life of 5730 years to date the object.
A Danger to DNA
Radioactivity is never good for living organisms. There are times that radioactive particles pass right through organisms with no effect but there are other times that they hit DNA or affect replicating cells. Bad things happen when DNA is exposed to radioactive particles. The usual results of moderate levels of radioactive particles are different types of cancer. Cells reproduce in ways that are not normal. High doses of radioactivity can kill a human within 24 hours. Medicine has learned how to use radioactivity to stop cancers. Since they know that excess levels of radioactivity can kills cells, doctors target areas of cancer with radioactivity to stop the cancer cells from dividing.
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