25.1. The Nucleus http://www.ck12.org
60
27 Co
∗→ 60
27 Co+γTo recap:
- Alpha decay produces the slowest-moving, most massive particles, helium nuclei.
- Beta decay produces fast-moving electrons.
- Gamma decay produces only radiation.
Alpha radiation, as it is sometimes called, usually cannot penetrate even a thin sheet of paper. Beta radiation can pass
through a thin piece of wood or a few millimeters of aluminum, and gamma radiation would go a few centimeters of
lead as shown inFigure25.3.
FIGURE 25.3
Penetrating abilities of alpha particles,
beta particles and gamma radiation.Generally, being exposed to alpha radiation is not harmful unless the radiation is produced by a source inside the
body.
This may occur, for example, if the radioactive element radon (a gas) is inhaled. Then the effects of alpha radiation
can be very serious. Radon is a known carcinogen.
Here is a story of the Russian spy, Alexander Litvinenko, who won asylum in Great Britain, only to have died in
2006 under “mysterious” circumstances, related to radiation poisoning induced by alpha-decay of polonium-210,
found in his body. Follow the link below to learn more.
http://en.wikipedia.org/wiki/Alexander_Litvinenko
An alpha particle possessing the same amount of energy as a beta particle or gamma ray can cause ten to twenty times
the damage to human cellular structure. The more massive, positively charged, alpha particle can cause numerous
ionizations (remove electrons from atoms). The electronic configuration of an atom (the number of and energy levels
of electrons) is responsible for all chemical interactions. Thus, a single alpha particle can cause the ionization of
many atoms and alter the chemical properties of atoms within cells. The greatest danger occurs when damaged cells
remain alive and continue to reproduce. Such altered, or mutated cells, do not perform their intended functions and
are generically called cancerous cells.
The effects of beta and gamma radiation on human health are also of serious concern since all types of radiation
have ionizing effects. This is why, for example, anytime an x-ray (yet another form of radiation dangerous to human
health) is taken for medical purposes, the patient is covered with a lead-lined apron. Lead is very dense and difficult
for the radiation to penetrate. The ionizing effect of gamma and x-ray radiation is thus significantly reduced by
passing through several millimeters of lead.
In addition to the ill effects of radiation, there are also some benefits. Ironically, the very cancers that may
be triggered by radiation can be fought by applying a narrowly directed radioactive beam to a cancerous area.