http://www.ck12.org Chapter 3. Chemical Interactions
TABLE3.13:Types of Radioactive Decay
Type Radiation Emitted
Alpha decay alpha particle (2 protons and 2 neutrons) + energy
Beta decay beta particle (1 electron or 1 positron) + energy
Gamma decay energy (gamma ray)It’s Elemental
Both alpha and beta decay change the number of protons in an atom’s nucleus, thereby changing the atom to a
different element. In alpha decay, the nucleus loses two protons. In beta decay, the nucleus either loses a proton
or gains a proton. In gamma decay, no change in proton number occurs, so the atom does not become a different
element.
Q:If the radioactive element polonium (Po) undergoes alpha decay, what element does it become?
A:From the periodic table, the atomic number of polonium is 84, so it has 84 protons. If it loses two protons through
alpha decay, it will have 82 protons. Atoms with 82 protons are the element lead (Pb).
Dangers of Radioactive Decay
The charged particles and energy emitted during radioactive decay can harm living things, but the three types of
radioactive decay aren’t equally dangerous. That’s because they differ in how far they can travel and what they can
penetrate. You can see this in theFigure3.109 and in the animation at the following URL: http://teachnuclear.ca/c
ontents/cna_radiation/gamma_rays/
FIGURE 3.109
Alpha particles can travel only a few centimeters through air. They can
burn the skin but not penetrate it. Beta particles can travel up to a meter
through air. They can penetrate and damage skin. Gamma rays can travel
thousands of meters through air. They can penetrate and damage cells
deep inside the body.Summary
- Radioactive decay is the process in which unstable nuclei of radioactive atoms become stable by emitting
charged particles and energy. - There are three types of radioactive decay: alpha decay, beta decay, and gamma decay. Alpha and beta decay
change one element into another. Gamma decay does not. - Radioactive decay can damage living things. Alpha decay is the least damaging, and gamma decay is the most
damaging.